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The Stability of Silver Nanoparticles in a Model of Pulmonary Surfactant
Abstract
The growing use of silver nanoparticles (AgNPs) in consumer products has raised concerns about their potential impact on the environment and human health. Whether AgNPs dissolve and release Ag+ ions, or coarsen to form large aggregates, is critical in determining their potential toxicity. In this work, the stability of AgNPs in dipalmitoylphosphatidylcholine (DPPC), the major component of pulmonary surfactant, was investigated as a function of pH. Spherical, citrate-capped AgNPs with average diameters of 14 ± 1.6 nm (n=200) were prepared by a chemical bath reduction. The kinetics of Ag+ ion release was strongly pH-dependent. After 14 days of incubation in sodium perchlorate (NaClO4) or perchloric acid (HClO4) solutions, the total fraction of AgNPs dissolved varied from ~10 % at pH 3, to ~2 % at pH 5, with negligible dissolution at pH 7. A decrease in pH from 7 to 3 also promoted particle aggregation and coarsening. DPPC (100 mg.L-1) delayed the release of Ag+ ions, but did not significantly alter the total amount of Ag+ released after two weeks. In addition, DPPC improved the dispersion of the AgNPs and inhibited aggregation and coarsening. TEM images revealed that the AgNPs were coated with a DPPC layer serving as a semi-permeable layer. Hence, lung lining fluid, particularly DPPC, can modify the aggregation state and kinetics of Ag+ ion release of inhaled AgNPs in the lung. These observations have important implications for predicting the potential reactivity of AgNPs in the lung and the environment.
... Several studies investigated silver nanoparticle dissolution in various surrogates of lung lining fluid (Leo et al., 2013;Maurer et al., 2014;Stebounova et al., 2011;Sweeney et al., 2016). In order to mimic lung lining fluid, these studies used buffer solutions (7 pH) and coated the nanoparticles with surfactants found in lung lining fluid, either dipalmitoylphosphatidylcholine (DPPC), the most common phospholipid pulmonary surfactant, or Curosurf®, a natural pulmonary surfactant prepared from porcine lungs (Botelho et al., 2016;Leo et al., 2013;Stebounova et al., 2011;Sweeney et al., 2016). ...
... Several studies investigated silver nanoparticle dissolution in various surrogates of lung lining fluid (Leo et al., 2013;Maurer et al., 2014;Stebounova et al., 2011;Sweeney et al., 2016). In order to mimic lung lining fluid, these studies used buffer solutions (7 pH) and coated the nanoparticles with surfactants found in lung lining fluid, either dipalmitoylphosphatidylcholine (DPPC), the most common phospholipid pulmonary surfactant, or Curosurf®, a natural pulmonary surfactant prepared from porcine lungs (Botelho et al., 2016;Leo et al., 2013;Stebounova et al., 2011;Sweeney et al., 2016). These studies observed low levels of silver nanoparticle dissolution (~0.4% by mass) when using pulmonary surfactants, and we used this factor to calculate nanoparticle dissolution in the pulmonary tract (Leo et al., 2013;Sweeney et al., 2016). ...
... In order to mimic lung lining fluid, these studies used buffer solutions (7 pH) and coated the nanoparticles with surfactants found in lung lining fluid, either dipalmitoylphosphatidylcholine (DPPC), the most common phospholipid pulmonary surfactant, or Curosurf®, a natural pulmonary surfactant prepared from porcine lungs (Botelho et al., 2016;Leo et al., 2013;Stebounova et al., 2011;Sweeney et al., 2016). These studies observed low levels of silver nanoparticle dissolution (~0.4% by mass) when using pulmonary surfactants, and we used this factor to calculate nanoparticle dissolution in the pulmonary tract (Leo et al., 2013;Sweeney et al., 2016). Additional factors that Smith affect nanoparticle dissolution, like ranges of nanoparticle concentrations (we predict ≤2.5 μg/mL nanoparticle concentration (see Results) compared to previously tested nanoparticle concentration of 25 μg/mL) with multiple particle diameters (prior studies tested 20 nm only), have not been robustly evaluated in lung lining fluids (Leo et al., 2013;Sweeney et al., 2016). ...
As encouraged by Toxicity Testing in the 21st Century, researchers increasingly apply high-throughput in vitro approaches to identify and characterize nanoparticle hazards, including conventional aqueous cell culture systems to assess respiratory hazards. Translating nanoparticle dose from conventional toxicity testing systems to relevant human exposures remains a major challenge for assessing occupational risk of nanoparticle exposures. Here, we explored existing computational tools and data available to translate nanoparticle dose metrics from cellular test systems to inhalation exposures of silver nanoparticles in humans. We used the Multiple-Path Particle Dosimetry (MPPD) Model to predict nanoparticle deposition of humans exposed to 20 and 110 nm silver nanoparticles at 0.9 μg/m³ over an 8 h period, the proposed National Institute of Occupational Safety and Health (NIOSH) recommended exposure limit (REL). MPPD predicts 8.1 and 3.7 μg of silver deposited in an 8 h period for 20 and 110 nm nanoparticles, respectively, with 20 nm particles displaying nearly 11-fold higher total surface area deposited. Peak deposited nanoparticle concentrations occurred more proximal in the pulmonary tract compared to mass deposition patterns (generation 4 vs. generations 20–21, respectively) due to regional differences in lung lining fluid volumes. Assuming 0.4% nanoparticle dissolution by mass measured in previous studies predicted peak concentrations of silver ions in cells of 1.06 and 0.89 μg/mL for 20 and 110 nm particles, respectively. Both predicted concentrations are below the measured toxic threshold of 1.7 μg/mL of silver ions in cells from in vitro assessments. Assuming 4% dissolution by mass predicted 10-fold higher silver concentrations in tissues, peaking at 10.6 and 8.9 μg/mL, for 20 and 110 nm nanoparticles respectively, exceeding the observed in vitro toxic threshold and highlighting the importance and sensitivity of dissolution rates. Overall, this approach offers a framework for extrapolating nanotoxicity results from in vitro cell culture systems to human exposures. Aligning appropriate dose metrics from in vitro and in vivo hazard characterizations and human pulmonary doses from occupational exposures are critical components for successful nanoparticle risk assessment and worker protection providing guidance for designing future in vitro studies aimed at relevant human exposures.
... Citratecoated particles are electrostatically stabilized by negatively charged anions. However, as the pH value decreases, the citrate-anion protonates, which causes the loss of stabilization [59]. In vivo AgNPs capped by citrate or PVP demonstrate the greater antibacterial activity against Salmonella, compared to uncapped AgNPs, which could be explained by minimal interaction with serum proteins. ...
... The surface charge of AgNPs becomes more negative at higher pH, as confirmed by the high zeta potential value equal to -32.5 mV, which promotes the stability of the suspension. Conversely, lower pH values of 5 and 3 are characterized by a decrease in zeta potential to -22.5 and -18.2 mV, which, therefore, reduces the repulsive forces and stability [59]. Moreover, small AgNPs have lower zeta potentials than large AgNPs; thus, small particles have less electrostatic repulsion and more rapid aggregation. ...
In the 21st century, a great interest is devoted to biomedical application of various nanoparticles, particularly, as a means of improving the effectiveness of therapy for different diseases. Silver nanoparticles (AgNPs) are the most studied and investigated type of nanoparticles. Due to the wide spectrum of their action, silver nanoparticles may be used both to influence pathogenic microorganisms and to improve the treatment of cancer. The basic physico-chemical characteristics and stabilizing agents play an important modifying role in the pharmacokinetics and pharmacodynamics of nanoparticles, determining the severity of the caused effect and their potential toxicity. This review summarizes the main physico-chemical properties of AgNPs and their impact on the biological effects. Additionally, biochemical and pathophysiological mechanisms of silver nanoparticles activity against various microorganisms and tumor cells are considered. Finally, we address the problems, associated with determining the optimal characteristics of nanoparticles, in order to increase their efficiency and reduce their toxicity for the macroorganism.
... Lipids account for over 90% of the total components of PS, and the formation of a lipid corona has been demonstrated for different types of NPs (22,29). Dipalmitoyl phosphatidylcholine (DPPC) is the predominant lipid component of PS, which consists of two palmitic acids attached to a phosphatidylcholine head-group (30). The presence of DPPC on SiNPs-PS or SiNPs-PS-MP was confirmed using thin-layer chromatography (TLC). ...
... Briefly, male C57BL/6 mice were randomly divided into two groups (SiNPs and SiNPs-PS) and intravenously injected with SiNPs and SiNPs-PS (1 μg/μL × 50 μL) through tail, respectively. Blood was collected at specific time points (5,30,60,120,240, and 480 min). Then, decomposition reagent containing 3 mL HNO 3 , 1 mL H 2 O 2 , and 1 mL HF was added into 0.5-mL blood sample, heated at 120°C for 30 min. ...
Nanoparticles (NPs) can make their way to the brain and cause in situ damage, which is a concern for nanomaterial application and airborne particulate matter exposure. Our recent study indicated that respiratory exposure to silica nanoparticles (SiO2 NPs) caused unexpected cardiovascular toxic effects. However, the toxicities of SiO2 NPs in other organs have warranted further investigation. To confirm the accumulation of SiO2 NPs in the brain, we introduced SiO2 NPs with different diameters into mice via intranasal instillation (INI) and intravenous injection (IVI) in parallel. We found that SiO2 NPs may target the brain through both olfactory and systemic routes, but the size of SiO2 NPs and delivery routes both significantly affected their brain accumulation. Surprisingly, while equivalent SiO2 NPs were found in the brain regions, brain lesions were distinctly much higher in INI than in the IVI group. Mechanistically, we showed that SiO2 NPs introduced via INI induced brain apoptosis and autophagy, while the SiO2 NPs introduced via IVI only induced autophagy in the brain.
... Lipids account for over 90% of the total components of PS, and the formation of a lipid corona has been demonstrated for different types of NPs (22,29). Dipalmitoyl phosphatidylcholine (DPPC) is the predominant lipid component of PS, which consists of two palmitic acids attached to a phosphatidylcholine head-group (30). The presence of DPPC on SiNPs-PS or SiNPs-PS-MP was confirmed using thin-layer chromatography (TLC). ...
... Briefly, male C57BL/6 mice were randomly divided into two groups (SiNPs and SiNPs-PS) and intravenously injected with SiNPs and SiNPs-PS (1 μg/μL × 50 μL) through tail, respectively. Blood was collected at specific time points (5,30,60,120,240, and 480 min). Then, decomposition reagent containing 3 mL HNO 3 , 1 mL H 2 O 2 , and 1 mL HF was added into 0.5-mL blood sample, heated at 120°C for 30 min. ...
Significance
To address a crucial knowledge deficiency concerning the correlation between nanoparticles (NPs) exposure and cardiovascular diseases, here we present a toxicological mechanism for inhaled NPs by delineating their interactions with the biomacromolecules encountered en route. In biological ambience, NPs are known to spontaneously adsorb proteins, thereby acquiring a new biological identity and further entailing pathological prospects. Here, we found that silica nanoparticles (SiNPs) specifically adsorbed apolipoprotein A-I (Apo A-I) in the blood to ameliorate their cytotoxicity, while a rapid clearance of SiNPs from the bloodstream depleted plasma Apo A-I and facilitated SiNPs-induced atherosclerosis. This study is a demonstration of the relationship between plasma protein adsorption and cardiovascular damage induced by engineered NPs.
... 18 Looking into the mechanism of action of the Ag NPs in releasing Ag + ions or formation of large aggregates that determines toxicity, these were protected by lung surfactant, such as dipalmitoylphosphatidylcholine (DPPC), and investigated as a function of pH. 19 The results helped understanding the stability of the Ag NPs in the deep lung. Prolonged research showed that the cytotoxicity of uncoated Ag NPs is greater than that of coated Ag NPs. ...
... Ag NPs coated with bio-compatible proteins, lipids, and surfactants show better results in cell viability. 19,20 Proteins form corona on the surface of the NPs, which, in turn, interacts with the cell membrane during cellular intake. 22−24 Internalization of the Ag NPs triggers ROS generation due to oxidation of Ag. ...
To enhance the interactivity with biological cells, we developed ultrasmall (5 nm in diameter) Ag NPs coated with a mixture of Tween-20 (Tw-20) surfactant and human serum albumin (HSA) or hemoglobin (Hb) proteins. These were tested with cancerous and healthy cell lines to investigate the therapeutic applicability. Using the established concept of generation of reactive oxygen species (ROS) and the ROS-induced oxidative stress in carcinogenic cells by Ag NPs, we found that the presently synthesized Ag NPs selectively destroyed the cancerous cells. A mixture of Tw-20 with protein, where the surfactant was in large excess, created a coating over the Ag NPs resulting weaker protein-protein interactions and facilitating interfacial protein-surfactant interactions, which leads to an increase in the film viscoelasticity to enhance the stability of the Ag NPs and cell viability. Moreover, this concept has been applied to drug delivery using a model fluorophore (fluorescein) on Ag NPs to explore the prospects in photodynamic therapy. The results are encouraging and deserve further investigation.
... In contrast, in alkaline pH ( Fig. 5(b)), the particles are once again presented in a small size and are impossible to visualize with backscattered electrons. This result is compatible with Leo et al. (2013) [48], whose synthesis of AgNPs in the presence of sodium citrate showed a high agglomeration of particles in lower pH values. ...
... In contrast, in alkaline pH ( Fig. 5(b)), the particles are once again presented in a small size and are impossible to visualize with backscattered electrons. This result is compatible with Leo et al. (2013) [48], whose synthesis of AgNPs in the presence of sodium citrate showed a high agglomeration of particles in lower pH values. ...
This study evaluated, through a central composite experimental design, the influence of silver nanoparticles (AgNPs) deposition, synthesized at different pH and silver concentration [Ag+], on the photocatalytic efficiency of self-assembled thin films (SATFs) of poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) and TiO2 over bezafibrate (BZF) drug. The SATFs were produced by dip coating on glass substrates using the layer-by-layer technique and were characterized by ultraviolet and visible absorption spectroscopy, scanning electron microscopy with a field emission gun and energy dispersive spectroscopy. The results revealed that the SATF that represents the optimum point of the central composite design (pH = 7.0 and [Ag+] =0.46 mmol L−1) reduced the initial concentration of BZF by 81.4 %. The presence of AgNPs on the polyelectrolytes/TiO2 thin film was responsible for an increase of 64 % in its photocatalytic efficiency when compared to the film containing only polyelectrolytes and TiO2. Silver is present mostly in the form of nanoparticle agglomerates with sizes under 90 nm. Moreover, the optimized SATF showed no reduction in its photocatalytic efficiency after four reuse cycles. Finally, the data set showed that the SATFs of this work possess a high potential for photo-oxidation, which makes them attractive for domestic and industrial wastewater treatment.
... To achieve suspensions with minimal nanoparticle aggregation, surface engineering strategies that favor or enhance interparticle repulsive forces are usually applied (31)(32)(33). Typically, this involves additives such as surfactants or electrolyte ions to envelop particle surfaces, imparting similar net charges that promote particle dispersion (34)(35)(36)(37)(38)(39)(40). An obvious drawback is the potential impact of the additive on surface structure, particle solubility, and active site availability, which can negatively affect target applications (41,42). ...
Nanoparticle aggregates in solution controls surface reactivity and function. Complete dispersion often requires additive sorbents to impart a net repulsive interaction between particles. Facet engineering of nanocrystals offers an alternative approach to produce monodisperse suspensions simply based on facet-specific interaction with solvent molecules. Here, we measure the dispersion/aggregation of three morphologies of hematite (α-Fe 2 O 3 ) nanoparticles in varied aqueous solutions using ex situ electron microscopy and in situ small-angle x-ray scattering. We demonstrate a unique tendency of (104) hematite nanoparticles to maintain a monodisperse state across a wide range of solution conditions not observed with (001)- and (116)-dominated particles. Density functional theory calculations reveal an inert, densely hydrogen-bonded first water layer on the (104) facet that favors interparticle dispersion. Results validate the notion that nanoparticle dispersions can be controlled through morphology for specific solvents, which may help in the development of various nanoparticle applications that rely on their interfacial area to be highly accessible in stable suspensions.
... During a new material's development, it is feasible to be produced under extremely controlled circumstances, usually in very small quantities. Exposures may happen during synthesis or downstream processes such as packaging, shipping, recovery, and storage once the substance enters commercial production 36 . Nanomaterials can be released intentionally in processes like contaminated land remediation or as waste or industrial pollutants into the air, soil, or water systems. ...
The toxicity of nanoparticles (NPs) is a critical research topic in nanotechnology, as it is essential to understand thehazards posed by the wide spectrum of NPs that vary in shape, size, and composition. Previous reviews have yet to thoroughlyexplore the Biological Effective Doses of NPs, which drive toxicity and are influenced by factors such as solubility, charge, shape,contaminants, and the ability of NPs to translocate from the deposition site in the lungs. This review aims to fill the gap in theliterature by providing an overview of the possible toxicity of nanoparticles in zebrafish during growth stages, with a focus onoxidative stress, and exploring the available modes of toxicity that are relevant to conventional pathogenic particles. This reviewalso discusses the effects of nanomaterials on the reproductive system in animal models, providing insight into the potential toxicityof nanoparticles in humans. This review aims to provide a comprehensive overview of the toxicity of nanoparticles and to criticallyexplore the challenges associated with implementing nanotechnology, particularly in the pharmaceutical development of noveltherapeutic products and regulatory issues. The review also considers recent uses and projected nanotechnology advancements,providing a basis for future research in this field. In conclusion, this review rectifies the lacunae in previously published reviews byproviding a comprehensive overview of the toxicity of nanoparticles and exploring the challenges associated with implementingnanotechnology. The aim and objective of this review are to provide a comprehensive understanding of the toxicity of nanoparticlesand to guide future research in this field.
... PDI values below 0.3 typically indicate a uniform distribution of particle sizes [35]. The values obtained are slightly higher than this threshold, which can be attributed to mild aggregation events that are common in metallic nanoparticles and depend on several chemical parameters of their immediate environment [36,37]. This may explain why particle size measurements obtained by this technique are much larger than expected. ...
The use of diverse Ag-based nanoparticulated forms has shown promising results in controlling viral propagation. In this study, a commercial nanomaterial consisting of ceramic-coated silver nanoparticles (AgNPs) was incorporated into thermoplastic polyurethane (TPU) plates using an industrial protocol, and the surface composition, ion-release dynamics and viricidal properties were studied. The surface characterization by FESEM-EDX revealed that the molar composition of the ceramic material was 5.5 P:3.3 Mg:Al and facilitated the identification of the embedded AgNPs (54.4 ± 24.9 nm). As determined by ICPMS, the release rates from the AgNP–TPU into aqueous solvents were 4 ppm/h for Ag and Al, and 28.4 ppm/h for Mg ions. Regarding the biological assays, the AgNP–TPU material did not induce significant cytotoxicity in the cell lines employed. Its viricidal activity was characterized, based on ISO 21702:2019, using the Spring viraemia of carp virus (SVCV), and then tested against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The results demonstrated that AgNP–TPU materials exhibited significant (75%) and direct antiviral activity against SVCV virions in a time- and temperature-dependent manner. Similar inhibition levels were found against SARS-CoV-2. These findings show the potential of AgNP–TPU-based materials as a supporting strategy to control viral spread.
... Nanotoxicology is very complex and multifaceted as it depends on a variety of physicochem ical and surface properties like their size, shape, charge, area, and reactivity. Furthermore, the interaction of ENMs with the environment may affect their bioavailability and stability (Leo et al., 2013;Leo et al., 2019). ...
... Zeta potential is an important indicator of the surface charge of nanoparticles (Kthiri et al., 2021). The surface charge of AgNPs is related to their dispersity and stability (Leo et al., 2013). The high value of the negative zeta potential indicates long-term stability and dispersion, lack of flocculation and the tendency to form agglomerates of biogenic AgNPs due to the repulsion of negatively charged particles (Skoglund et al., 2017;Win et al., 2020;Foujdar et al., 2021). ...
... ±2 mJ g −1 to -179.5/-173.6 ±1 mJ g −1 ) and generated stable dispersion with an average hydrodynamic size of 110-190 nm and larger negative surface charge (-30 mV) compared with pristine TiO 2 NPs (-20 mV). Similarly, Leo et al. [76] showed that DPPC inhibited aggregation of the AgNPs and improved dispersion, and more interestingly, DPPC appeared to form a semi-permeable layer, modifying the release kinetics of Ag + ion from AgNPs in perchlorate acid solution (pH = 3.0 or 5.0). In addition, DPPC adsorption could reduce NPs internalization and cytotoxicity in lung tissue cells. ...
Pulmonary drug delivery has drawn great attention due to its targeted local lung action, reduced side effects, and ease of administration. However, inhaled nanoparticles (NPs) could adsorb different pulmonary surfactants depending on their physicochemical properties, which may impair the physiological function of the pulmonary surfactants or alter the fate of the NPs. Thus, the objective of this review is to summarize how the physicochemical properties of NPs affecting the physiological function of pulmonary surfactants and their fate. First of all, the composition and characteristics of pulmonary surfactants, methods for studying pulmonary surfactant interaction with NPs are introduced. Thereafter, the influence of physicochemical properties of NPs on hydrophobic protein adsorption and strategies to decrease the interaction of NPs with pulmonary surfactants are discussed. Finally, the influence of physicochemical properties of NPs on lipids and hydrophilic protein adsorption and consequently their fate is described. In conclusion, a better understanding of the interaction of NPs with pulmonary surfactants will promote the faster development of safe and effective nanomedicine for pulmonary drug delivery.
Statement of Significance
: Drug delivery carriers often face complex body fluid components after entering the human body. Pulmonary surfactants diffuse at the lung gas-liquid interface, and particles inevitably interact with pulmonary surfactants after pulmonary nanomedicine delivery. This review presents an overview of how the physicochemical properties of nanoparticles affecting their fate and physiological function of pulmonary surfactants. We believe that the information included in this review can provide important guiding for the development of safe and effective pulmonary delivery nanocarriers.
... In these, a concentration-dependent increase in solubility was observed with the addition of DPPC (Davies and Feddah 2003;Son and McConville 2009). Likewise, DPPC was shown to stabilise Ag NPs against aggregation, without significantly effecting the total Ag release (Leo et al. 2013). This was consistent with results from Maccuspie et al. (2011) who noted a subtle stabilisation of Ag NPs accredited to DPPC, however higher stability was found with the inclusion of bovine serum albumin (BSA). ...
The use of simulated biological fluids (SBFs) is a promising in vitro technique to better understand the release mechanisms and possible in vivo behaviour of materials, including fibres, metal-containing particles and nanomaterials. Applications of SBFs in dissolution tests allow a measure of material biopersistence or, conversely, bioaccessibility that in turn can provide a useful inference of a materials biodistribution, its acute and long-term toxicity, as well as its pathogenicity. Given the wide range of SBFs reported in the literature, a review was conducted, with a focus on fluids used to replicate environments that may be encountered upon material inhalation, including extracellular and intracellular compartments. The review aims to identify when a fluid design can replicate realistic biological conditions, demonstrate operation validation, and/or provide robustness and reproducibility. The studies examined highlight simulated lung fluids (SLFs) that have been shown to suitably replicate physiological conditions, and identify specific components that play a pivotal role in dissolution mechanisms and biological activity; including organic molecules, redox-active species and chelating agents. Material dissolution was not always driven by pH, and likewise not only driven by SLF composition; specific materials and formulations correspond to specific dissolution mechanisms. It is recommended that SLF developments focus on biological predictivity and if not practical, on better biological mimicry, as such an approach ensures results are more likely to reflect in vivo behaviour regardless of the material under investigation.
... Some AgNPs agglomerated inside vesicles ( Fig. 3a and b), possibly due to the lower pH of the intravesicular environment and thermodynamic driving force to minimize their total surface energy. 36 Inside the ASM cells, the morphology of the AgNSs and S-and L-AgNWs was altered and many smaller, diffuse particles surrounded them, indicating dissolution and re-precipitation (Fig. 3b, d and f, respectively). Qualitatively, we observed that the AgNSs and S-AgNWs were avidly internalised by the ASM cells (Fig. 3a, c and d), whereas L-AgNWs were rarely internalised by the cells. ...
Sulfidation by biogenic H 2 S outcompetes dissolution of silver nanostructures, thus reducing their toxicity in airway smooth muscle cells.
... The stability of silver nanomaterials is a critical factor affecting the antibacterial effect of silver nanomaterials. 55 Nevertheless, no publication has reported their long-term stability, and few studies have investigated the long-term antibacterial effect of silver nanomaterials. ...
Objective
The aim of this concise review is to summarize the use of silver nanomaterials for caries prevention.
Methods
Two researchers independently performed a literature search of publications in English using Embase, Medline, PubMed, and Scopus databases. The keywords used were (silver nanoparticles OR AgNPs OR nano silver OR nano-silver) AND (caries OR tooth decay OR remineralisation OR remineralization). They screened the title and abstract to identify potentially eligible publications. They then retrieved the full texts of the identified publications to select original research reporting silver nanomaterials for caries prevention.
Results
The search identified 376 publications, and 66 articles were included in this study. The silver nanomaterials studied were categorized as resin with silver nanoparticles (n=31), silver nanoparticles (n=21), glass ionomer cement with silver nanoparticles (n=7), and nano silver fluoride (n=7). Most (59/66, 89%) studies investigated the antibacterial properties, and they all found that silver nanomaterials inhibited the adhesion and growth of cariogenic bacteria, mainly Streptococcus mutans. Although silver nanomaterials were used as anti-caries agents, only 11 (11/66, 17%) studies reported the effects of nanomaterials on the mineral content of teeth. Eight of them are laboratory studies, and they found that silver nanomaterials prevented the demineralization of enamel and dentin under an acid or cariogenic biofilm challenge. The remaining three are clinical trials that reported that silver nanomaterials prevented and arrested caries in children.
Conclusion
Silver nanoparticles have been used alone or with resin, glass ionomer, or fluoride for caries prevention. Silver nanomaterials inhibit the adhesion and growth of cariogenic bacteria. They also impede the demineralization of enamel and dentin.
... The zeta potential of Ag NPs decreased monotonically from − 12.1 mV at pH 7.0 to − 24.4 mV at pH 11.0, which confirmed the negatively charged groups on the surface of Ag NPs. Gao et al. reported that the dispersion and stability of Ag NPs mainly attribute to the surface charge [31]. The presence of negatively charged groups improves the stability and dispersion of Ag NPs in aqueous solutions [32]. ...
Biosynthesis for the preparation of antimicrobial silver nanoparticles (Ag NPs) is a green method without the use of cytotoxic reducing and surfactant agents. Herein, shape-controlled and well-dispersed Ag NPs were biosynthesized using yeast extract as reducing and capping agents. The synthesized Ag NPs exhibited a uniform spherical shape and fine size, with an average size of 13.8 nm. The biomolecules of reductive amino acids, alpha-linolenic acid, and carbohydrates in yeast extract have a significant role in the formation of Ag NPs, which was proved by the Fourier transform infrared spectroscopy analysis. In addition, amino acids on the surface of Ag NPs carry net negative charges which maximize the electrostatic repulsion interactions in alkaline solution, providing favorable stability for more than a year without precipitation. The Ag NPs in combination treatment with ampicillin reversed the resistance in ampicillin-resistant E. coli cells. These monodispersed Ag NPs could be a promising alternative for the disinfection of multidrug-resistant bacterial strains, and they showed negligible cytotoxicity and good biocompatibility toward Cos-7 cells.
... There are both pros and cons in choosing Au or Ag as SERS substrate. Between Ag and Au NPs of identical shapes and sizes, Ag NPs show higher SERS enhancement than Au NPs, but Au NPs show more stability, homogeneity and biocompatibility than Ag NPs as Ag gets oxidized very easily and becomes toxic [28]. ...
Here we report a simple low-cost method to produce surface-enhanced Raman scattering (SERS) substrates with improved efficiency and high sensitivity towards uric acid and ascorbic acid sensing using non-enzymatic amperometric electrochemical method. Trisoctahedral gold (Au) core-silver (Ag) shell cubical shaped nanoparticles were synthesized simply by varying the surfactant in the reaction medium, and afterwards we made them hollow by galvanic displacement reaction. Spherical core-shell nanoparticles (both solid and hollow) were also prepared to compare results with cubical one. We have performed transmission electron microscopy (TEM) studies to understand the morphology of these nanoparticles and UV–vis–NIR and Raman spectroscopy studies to understand optical properties. We have obtained a huge SERS enhancement (~109) for hollow Au@Ag nanocube using 4-mercapto benzoic acid (4-MBA) as analyte. Because of the very thin Ag shell wall, both core Au and shell Ag interacts with the incoming electromagnetic wave, and also due to the presence of multiple sharp edges and corners in both core and shell part of the nanoparticles there is a large enhancement of the electromagnetic field. We have performed cyclic voltammetry study using the nanoparticles as electrode to understand how interfacial charge transfer and electron accumulation is happening in between an electrode and electrolyte interface and we have obtained a very high current response for hollow core-shell nanocube due to more surface area. High current response with voltage enable us to use hollow core-shell nanocubes as non-enzymatic electrochemical sensor for sensing uric acid (UA) and ascorbic acid (AA). We found a good sensitivity (1.509 μAmM−1cm−2 and 209.027 μAmM−1cm−2 for UA and AA, respectively) and very low detection limit (0.36 μM and 0.019 μM for UA and AA, respectively) towards sensing, which allows us to use Au@Ag hollow nanocube as a good UA and AA sensors.
... The similar results were obtained in this study. The kinetics of Ag þ release from Ag nanomaterials were strongly pH-dependent (Leo et al., 2013). In a lysosome acidic environment, Ag nanomaterials were found to be less stable, leading to more Ag þ released (Setyawati et al., 2014;Jimeno-Romero et al., 2017). ...
Long silver nanowires (AgNWs, >5 μm) have shown promising applications in next generation biomaterials. However, the toxicity of long AgNWs is not well characterized in terms of their size. In this study, five AgNWs types, including SAgNW30 (length: 5-10 μm; diameter: 30 nm), MAgNW30 (length: 20-30 μm; diameter: 30 nm), LAgNW30 (length: ∼100 μm; diameter: 30 nm), LAgNW50 (length: ∼100 μm; diameter: 50 nm), and LAgNW100 (length: ∼100 μm; diameter: 100 nm), were used to investigate the size-dependent phagocytosis and cytotoxicity in macrophage. It showed that SAgNW30, MAgNW30, LAgNW30 can be fully phagocytosed by macrophages, but LAgNW50 and LAgNW100 frustrated the phagocytosis. It demonstrated that LAgNW30 can be internalized into macrophage in a curly manner. The size-dependent cytotoxicity was observed in cell viability, apoptosis, mitochondrial damage, phenotypic transition, and inflammatory response in AgNWs-treated macrophage. The AgNWs-induced cytotoxicity was depended on their length and diameter, increased gradually in the order of SAgNW30 > MAgNW30 > LAgNW30 > LAgNW50 > LAgNW100. The findings presented here will assist in the evaluation of the size-dependent cytotoxicity mediated by long AgNWs.
... It should be highlighted that the nanofluid is commercialized with a pH of 3.1 (zeta potential of 22.60 mV). Different results were obtained by Sadowski et al. (2008), Elzey and Grassian (2010), and Leo et al. (2013) for silver nanoparticles in suspension. In all cases, the charge at the surface was negative and the isoelectric point was located at the acid pH of 2.0, 2.5 and 3.0, respectively. ...
The rheological behavior of an aqueous suspension of silver nanoparticles stabilized with aminosilane-based surfactant flowing under confinement was investigated. Three stability levels were defined based on the zeta potential: high (41.73 mV, pH 4.3), medium (10.44 mV, pH 7.4), and low (0.74 mV, pH 8.6). Furthermore, the preliminary investigation showed that the surface charge remained positive, and the formation of agglomerates was not observed. Due to the particle coating and the ionization of the amino groups of the surfactant an electrosteric stabilization was evidenced. Shear rates ranging from 50 to 1000 s-1 and shear stresses between 0.02 and 0.2 Pa, at the temperatures of 15, 25 and 35 ºC, were evaluated with the nanofluid flowing in microchannels with a gap of 100, 300 and 500 µm. A trend to dilatant behavior was observed at high shear rate and a slit size of 500 µm, while Newtonian behavior was predominant at lower slit sizes. A reduction of 47.3% was noticed at 25 ºC with the variation in the slit size from 500 to 300 µm. Furthermore, the viscosity of the nanofluid decreased as much as 60% when the slit size was reduced from 500 to 100 µm.
... The lipid-coating on NPs can be suitably designed for controlled release of active molecules embedded among the lipids. DPPC molecules were used for AgNPs and AuNPs thermo-responsive coating (Leo et al., 2013). DPPC is a thermoresposive phospholipid, which has a transition temperature from the gel to the liquid phase at 41 • C. DPPC phase transition can be used to trigger the release of active molecules: DPPC in the gel-phase forms a particularly rigid bilayer, while the transition to the more-fluid liquid phase makes the DPPC coating prone to release the molecular cargo (Kang and Ko, 2015;Hamilton, 2017). ...
Inorganic nanoparticles (NPs) exhibit relevant physical properties for application in biomedicine and specifically for both the diagnosis and therapy (i.e. theranostic) of severe pathologies, such as cancer. The inorganic NP core is often not stable in aqueous suspension and can induce cytotoxic effects. For this reason, over the years, several coating strategies were suggested to improve the NP stability in aqueous solutions as well as the NP biocompatibility. Among the various components which can be used for NP coatings, lipids, and in particular phospholipids emerged as versatile molecular building blocks for the production of NP coatings suitable for biomedical application. The recent synthetic efforts in NP lipid coatings allows today to introduce on the NP surface a large variety of lipid molecules eventually in mixture with amphiphilic or hydrophobic drugs or active molecules for cell targeting. In this review, the most relevant examples of NP lipid-coatings are presented and grouped in two main categories: supported lipid bilayers (SLB) and hybrid lipid bilayers (HLB). The discussed scientific cases take into account the most commonly used inorganic NP for biomedical applications in cancer therapy and diagnosis.
... Silver is the main products among all nanoparticles and used widely in many applications because of its broad spectrum properties, in addition to inflammatory activity the anti-microbial activity used against bacteria, viruses and fungi 4 . periostin is a useful biomarkers for bronchial asthma and it has been shown to down regulate of immune responses such as (IL-4) and (IL-13) and it can predict the hypo responsiveness to corticosteroid inhalation in asthma patients 5 . Galectin-3 are one of the most biomarkers which have functions in variety of biological processes such as allergic pathology and inflammation also, the Galectin-3 belong to the family of B-galactose side binding animal lectins 6 . ...
In the current study ninety one of male mice weighting (25-30 g) aged (15-17) weeks at the animal house faculty of science / university of Kufa during the period from January 2017 to September 2017. This study included some physiological and histological criteria to evaluate the protective role of omega-3(2 and 3 mg/kg) and silver nanoparticles (5 and 10 mg/kg) against asthma that induced by ovalbumin. The animals experimental are divided into 16 groups (n= 6 mice per each group) for duration of one and two months. The results showed significant increase (p<0.05) in the leukocyte count (eosinophil, neutrophil, lymphocyte, monocyte) in asthma group as compared with control group.Also,the results showed significant decrease (p<0.05) in the leukocyte count in the treated group of omega-3 and silver nanoparticles for both concentration as compared with asthma group. The result sowed significant increase(p<0.05) in the serum level of periostin and Galectin-3 and Interleukin-33 in asthma group as compared with control group. The histological study of lung tissue revealed that induced the tissue with ovalbumin caused necrosis, degeneration and increase of mucous in bronchiole as well as acute inflammation around bronchioles while the effect of ovalbumin in trachea tissue were sluphing, necrosis and degeneration around the epithelium of bronchioles. © 2018, International Journal of Pharmaceutical Quality Assurance. All rights reserved.
... Freshly prepared citrate-coated AgNPs were stable not only during a 24 h period, as can be seen from the results presented in Table 1 and Fig. 3, but also for a much longer time (more than 3 months), as expected from the large negative ζ potential value, i.e. −45.5 ± 0.7 mV. As the ζ potential is related to the electrical potential at the interface between the diffuse ion layer surrounding the NPs and the bulk solution, 48 the high absolute ζ potential value provides a repulsive force keeping the NPs away from each other. Thus, a ζ potential value close to zero means that the repulsion between NPs decreases as does the stability of the NP dispersion. ...
Due to the wide and increasing application of engineered silver nanoparticles (AgNPs) in commercial products, their release and disposal into aquatic environmental compartments is unavoidable. The final environmental fate of AgNPs depends on their stability, behavior and lifetime in a particular system. This study aimed to systematically investigate the aggregation and dissolution behavior of AgNPs in model aquatic systems including a range of different pH, different concentrations of mono- and divalent electrolytes, and the presence of non-ionic, anionic and cationic surfactants used in commercial detergents. The investigation was performed by a combination of surface plasmon resonance (SPR) techniques, dynamic light scattering (DLS) and electrophoretic light scattering (ELS) methods, inductively coupled plasma mass spectroscopy (ICPMS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The obtained results highlighted the importance of pH, ionic strength and interaction with surfactants relevant to the laundry cycle on the stability and environmental fate of citrate-coated AgNPs. An important implication of this study is that the interaction of AgNPs with surfactants present in wastewater effluents could potentially become more environmentally hazardous due to the increased persistence and dissolution of AgNPs.
... 30,31 Pulmonary surfactants were reported to interact with AgNPs and AgNWs and affect their aggregation and bioavailability. 14,32,33 However, the impacts of various surfactants on the environmental transformation of AgNWs, especially their oxidative dissolution and sulfidation, are largely unclear. ...
Due to the excellent properties, silver nanowires (AgNWs) are applied increasingly in many optical and electronic products, and may be inevitably discharged in aquatic environments. Dissolution and sulfidation are two of the most important processes of AgNWs occurring in aquatic environments and may significantly affect their fate and toxicities. This study aimed to investigate the impacts of four types of surfactants on the dissolution and sulfidation of AgNWs. Anionic, zwitterionic, and nonionic surfactants, including sodium dodecylbenzenesulfonate, cetyl betaine, and glycerol monostearate, did not affect the dissolution and sulfidation of AgNWs. However, the cationic surfactants (cetyltrimethylammonium bromide, cetyltrimethylammonium nitrate and benzyldimethyldodecylammonium nitrate) promoted the dissolution and sulfidation of AgNWs significantly. The cationic surfactants, especially cetyltrimethylammonium bromide, preferred to bind with the (111) planes of AgNWs, leading to the corrosion of initial wire structure of AgNWs to shorter nanorods. The increased surface area of AgNWs resulted faster dissolution. The dissolved Ag⁺ ions reacted with sulfide quickly, leading to faster sulfidation of AgNWs. In addition, the cationic surfactants interacted with AgNWs and decreased the electrostatic repulsion between the sulfide ions and the surface of AgNWs, thus promoting the direct oxysulfidation. As a consequence, cationic surfactants facilitated the sulfidation of AgNWs in a greater extent than dissolution. The interaction of AgNWs and surfactants could significantly affect their bioavailability and ecotoxicities in aquatic environments.
Upon addition of cell lysates to the sample pad, SERS probes located on the conjugation pad would bind to target miRNAs, leading to no captured SERS probes and no discernible color change on the T line.
Gold nanoparticles (AuNPs), universally regarded as colorimetric signal reporters, are widely employed in lateral flow immunoassays (LFIAs). However, it is difficult for AuNPs‐LFIA to achieve a wide range and sensitive detection. Herein, novel coral‐like hollow gold nanospheres (CHGNPs) are synthesized. The growth of gold nanospheres can be regulated to obtain a multibranched and hollow construction. The obtained CHGNPs possess intense broadband absorption across the visible to near‐infrared region, exhibiting a high molar extinction coefficient of 14.65 × 10 ¹¹ M ⁻¹ cm ⁻¹ and a photothermal conversion efficiency of 79.75%. Thus, the photothermal/colorimetric dual‐readout LFIA is developed based on CHGNPs (CHGNPs‐PT‐LFIA and CHGNPs‐CM‐LFIA) to effectively improve the detection sensitivity and broaden the detection range in regard to sulfonamides (SAs). The limits of detection of the CHGNPs‐PT‐LFIA and CHGNPs‐CM‐LFIA reached 1.9 and 2.8 pg mL ⁻¹ for the quantitative detection of sulfaquinoxaline, respectively, which are 6.3‐fold and 4.3‐fold lower than that of the AuNPs‐LFIA. Meanwhile, the CHGNPs‐PT‐LFIA broadened the detection range to three orders of magnitude, which ranged from 2.5 to 5000 pg mL ⁻¹ . The synthesized photothermal CHGNPs have been proven effective in improving the performance of the LFIA and provide a potential option for the construction of sensing platforms.
Recently, there has been a growing interest in silver nanoparticles (AgNPs) and their biomedical applications. Nevertheless, the clinical translation of such a promising technology into the global healthcare market encounters multiple obstacles. In the current chapter, we put some light on the market status and clinical profile of AgNPs as well as the technical, industrial, and regulatory challenges hampering their translation from the bench to the bedside. Then, some promising advancements that enable the clinical translation of AgNPs are highlighted, including the innovative high-throughput production technologies and the recruitment of AgNPs into the battle against the emerging infectious diseases and pandemics. Furthermore, AgNPs are compared versus other competitive nanotechnologies from a technical and clinical perspective. Lastly, we inspire the key aspects that should be considered for the successful translation of this area of endeavor into the clinics and the healthcare market.
Nanotechnology is the state-of-the-art technology providing new horizons of ideas and scope to unlimited possibilities in almost all genres of day-to-day life ranging from diagnostic, therapeutic, agricultural, chemical to microelectronics, sensors, etc. In this connection, one of the main concerns regarding the metal-oxide nanoparticles is their synthesis, application in a safe mood to protect the overall toxic impact on the food web. To resolve this concern, a greener and cleaner method of producing the nanoparticles is being looked upon as a favorable alternative more commonly referred to as green chemistry or green synthesis. The metal-oxide nanoparticles synthesized from biological sources have demonstrated fulfilling properties and shown antibacterial, antiviral, antifungal, drug delivery, catalytic activity, etc., response. In this chapter, the role of fruits and their wastes in the green synthesis of metal-oxide nanoparticles is discussed. This could efficiently reduce the cost and is safer for the environment thus allowing us to implore more on their benefits without impending much harm to the environment.KeywordsNanotechnologyFlavonoidsAnti-microbialPolyphenolsDrug deliveryBiosensor
Nanotechnology has been a promising technological application where the usage of nanoparticles (NPs) in commercial and household operations has grown exponentially. The unique and inherent properties of different nanomaterials (NMs) have greatly impacted many fields. However, the increased use of NPs is being impeded by the possible toxic concerns on the environment because of their deliberate and accidental release. The size and form of NMs and their concentration, period of exposure effect, dosage, surface area, and surface functionalization significantly impact their behavior. Therefore, NMs can cause beneficial and harmful effects on niches including plants, animals, and microorganisms as well as on humans by interacting via diverse mechanisms. Hence, nanotechnology has become a double-edged sword that requires assessing its potential risk factors on all forms of life for its sustainable use. Therefore, this chapter elaborates on future prospects and risk factors of frequently used NPs on different trophics in the biosphere.KeywordsTitanium oxide NPsCopper NPsSilver nanoparticlesZinc oxide NPsIron oxide NPs
Viral and bacterial infections that are caused by biomedical devices, implants, or hospitals can be serious and even deadly. Advances in nanotechnology and biological sciences have made it possible to create smart surfaces for decreasing or inhibiting infections. Surface functionalization is aimed at adding intended reactive functional groups for targeting a cell or tissue in the human body. Polymer-based coatings are utilized to modify surface properties to meet certain requirements or include additional functionalities in terms of providing cell proliferation, tissue growth, repair, and delivery of biomolecules, such as growth factors, active molecules, antimicrobial agents, and drugs. In the circumstances of the COVID-19 viral pandemic, polymer-based coatings are gaining increased importance for biomedical devices, masks, and other equipment. In this chapter, the importance of antiviral and antimicrobial polymer-based surface coatings which are generated from functionalized nanoparticles is emphasized and evaluated with important examples.
Decades of nanotoxicology research have generated extensive and diverse data sets. However, data is not equal to information. The question is how to extract critical information buried in vast data streams. Here we show that artificial intelligence (AI) and molecular simulation play key roles in transforming nanotoxicity data into critical information, i.e., constructing the quantitative nanostructure (physicochemical properties)-toxicity relationships, and elucidating the toxicity-related molecular mechanisms. For AI and molecular simulation to realize their full impacts in this mission, several obstacles must be overcome. These include the paucity of high-quality nanomaterials (NMs) and standardized nanotoxicity data, the lack of model-friendly databases, the scarcity of specific and universal nanodescriptors, and the inability to simulate NMs at realistic spatial and temporal scales. This review provides a comprehensive and representative, but not exhaustive, summary of the current capability gaps and tools required to fill these formidable gaps. Specifically, we discuss the applications of AI and molecular simulation, which can address the large-scale data challenge for nanotoxicology research. The need for model-friendly nanotoxicity databases, powerful nanodescriptors, new modeling approaches, molecular mechanism analysis, and design of the next-generation NMs are also critically discussed. Finally, we provide a perspective on future trends and challenges.
Silver nanoparticles (AgNPs) are useful in various applications due to their unique chemical and physical
properties. Therefore, it is important to understand the stability of AgNPs for the development of
practical applications. Differently functionalised AgNPs will have different physicochemical properties.
This will lead to a variation in the toxicity of these NPs. Different functional groups (FGs) can form
coordination bonding or electrostatic interactions with AgNPs. In this study, three different sizes of
AgNPs were functionalised by PEG molecules containing five different FGs including methyl, carboxyl,
amine, hydroxyl and biotin to investigate the stability of AgNPs in terms of size and FG. The stability
was determined by calculating the binding energy of the PEGylated-AgNP system. The results indicate
that the stability increases with size, while the influence of the FG was observed to be size-dependent.
Viral and bacterial infections that are caused by biomedical devices, implants, or hospitals can be serious and even deadly. Advances in nanotechnology and biological sciences have made it possible to create smart surfaces for decreasing or inhibiting infections. Surface functionalization is aimed at adding intended reactive functional groups for targeting a cell or tissue in the human body. Polymer-based coatings are utilized to modify surface properties to meet certain requirements or include additional functionalities in terms of providing cell proliferation, tissue growth, repair, and delivery of biomolecules, such as growth factors, active molecules, antimicrobial agents, and drugs. In the circumstances of the COVID-19 viral pandemic, polymer-based coatings are gaining increased importance for biomedical devices, masks, and other equipment. In this chapter, the importance of antiviral and antimicrobial polymer-based surface coatings which are generated from functionalized nanoparticles is emphasized and evaluated with important examples.
Knowledge of the fate and transport of metal-organic frameworks (MOFs) in porous media is essential to understanding their environmental impacts. However, to date, the transport mechanisms of MOFs are not fully revealed. Meanwhile, surfactants can promote MOFs dispersion by forming a stable suspension. They also allow MOFs to migrate in the aqueous environment, which would increase the risks of MOFs being exposed to human health and the ecological environment. In this study, the effect of surfactants type and nanoparticle (NP) concentrations (50, 100, and 200 mg/L) were investigated using a sand column to study the transportability of ZIF-8 NPs in saturated porous media. Surfactants used were categorized into three groups, including cationic surfactants (CTAB, DTAB), anionic surfactants (SDBS, SDS), and nonionic surfactants (Tween 80, Tween 20). Experimental results showed that the ionic surfactants significantly increased the transportability of ZIF-8 NPs. Furthermore, a low concentration of NPs tended to break through the column under ionic surfactant conditions, and the maximum effluent recovery of ZIF-8 NPs (50 mg/L) was 87.4% in the presence of SDS. Nevertheless, ZIF-8 NPs tended to deposit in the inlet of the sand column in the presence of nonionic surfactants due to hydrodynamic bridging and straining. This research provides a comprehensive understanding of the deposition mechanism of ZIF-8 NPs as affected by surfactant types and NP concentrations. Most importantly, the study highlights those ionic surfactants had a significant impact on the mobility of ZIF-8 NPs, which arouses attention to the ecological and human health risk assessment related to the manufacturing of MOFs with the aid of various dispersing agents.
Iron oxide nanoparticles (IONPs) are one of the most important components in airborne particulate matter that originally generated from traffic emission, iron ore mining, coal combustion and melting of engine fragments. Once IONPs entered respiratory tract and deposit in the alveoli, they may interact with pulmonary surfactant (PS) that distributed in the alveolar lining. Thereafter, it is necessary to investigate the interaction of inhaled IONPs and PS, which helps the understanding of health risk of respiratory health induced by IONPs. Using dipalmitoyl phosphatidylcholine (DPPC), the major components of PS, as a lipid model, we explored the interaction of DPPC with typical IONPs, Fe3O4 NPs and amino-functionalized analogue (Fe3O4–NH2 NPs). DPPC was readily adsorbed on the surface of both IONPs. Although DPPC corona depressed the cellular uptake of IONPs, [email protected] complexes caused higher cytotoxicity toward RAW 264.7 macrophages, compared to pristine IONPs. Mechanistic studies have shown that IONPs react with intracellular hydrogen peroxide, which promotes the Fenton reaction, to generate hydroxyl radicals. Iron ions could oxidize lipids to form lipid peroxides, and lipid hydroperoxides will decompose to generate hydroxyl radicals, which further promote cellular oxidative stress, lipid accumulation, foam cell formation, and the release of inflammatory factors. These findings demonstrated the phenomenon of coronal component oxidation, which contributed to IONPs-induced cytotoxicity. This study offered a brand-new toxicological mechanism of IONPs at the molecular level, which is helpful for further understanding the adverse effects of IONPs.
The increasing negative effects of nanomaterials on humans and the environment have led to the increase in a new subtopic in the branch of nanotechnology, known as “nanotoxicology.” The issue of toxicity of nanomaterials has been a relatively new topic of concern with regard to nanotechnology, and this is because of the lack of techniques and experimental conditions in order to evaluate and monitor nanotoxicity. With the increase in concerns related to nanotoxicity, many global organizations have taken up the initiative to spread awareness and to design various strategies to assess the toxic effect of nanomaterials on human health and the environment. Nanoparticles can be produced by a variety of physical, chemical, and biological methodologies. Researchers have also been interested in trying to find out many new and interesting ways to synthesize nanoparticles for varied particle applications. The current chapter describes many such aspects of nanotoxicology including exposure, mechanism, and effects on human health.
The objective of this study was to evaluate the antagonistic effect of emerging pollutants of zinc oxide nanoparticles (ZnO NPs) and sodium dodecyl sulfate (SDS) on anaerobic digestion and explore their potential mechanism. The results indicated that at a low inhibitory concentration of ZnO NPs (1.0 mM), the practical co-inhibition was decreased by 24% and 18% in co-existence of 50 mg/L SDS and 300 mg/L SDS, respectively. More importantly, the co-existence of 300 mg/L SDS greatly enhanced methanogenesis of organics in seriously inhibited case (2.0 mM of ZnO NPs). The microbial community analysis showed that co-existed SDS enhanced the growth of Methanothrix, Methanosarcina and Methanobacterium. The antagonistic enhancement could be attributed to the net charge reversal, partially agglomeration of ZnO NPs and/or reduction of Zn2+ release in the presence of SDS. These findings could provide useful information for evaluating the co-inhibition of SDS and ZnO NPs on biological processes.
This study considered the stability of nickel oxide nanoparticles (nNiO) in seawater including their ability of aggregation and ion release. Furthermore, the relationship between these properties and their toxicity on marine algae Chlorella vulgaris was investigated. The results showed nNiO inhibited the growth of algal cells and decreased their chlorophyll content, which was due to the shading effects by aggregation of nNiO in seawater. Moreover, the release of Ni2+ depended on concentration of the nNiO solution. About 1.63% Ni2+ (varied from 0.89 to 3.63%) was detected and it may mediate the generation of ROS under both visible light and ultraviolet (UV) irradiation, which resulted in oxidative stress in algae. Therefore, the stability of nNiO in water affected its toxicity, which should be considered when assessing the nano-pollution risks in aquatic ecosystem.
The rapid development of nanotechnology is opening a huge world of promising possibilities in healthcare, but this is also increasing the necessity to study the potential risk of nanoparticles on public health and the environment. Since the main route for airborne particles to enter into our organism is through the lungs, it has become essential to prove that the nanoparticles generated by human activities do not compromise the respiratory function. This review explains the key role of pulmonary surfactant to sustain the normal function of breathing, as well as the stability and immunity of lungs. Particular emphasis is made on the importance of analysing the features of nanoparticles, defining their interactions with surfactant and unravelling the mutual effects. The implication of the nanoparticle-surfactant interaction on the function and fate of both structures is described, as well as the main in vitro methodologies used to evaluate this interaction. Finally, the incorporation of pulmonary surfactant in appropriate in vitro models is used in order to obtain an extensive understanding of how nanoparticles may act in the context of the lung. The main goal of this review is to offer a general view on inhaled nanoparticles and their effects on the structure and function of lungs derived from their interaction with the pulmonary surfactant system.
Silver and silver nanoparticles (AgNPs) exhibit antimicrobial properties against some bacteria, fungi and viruses, however, the ever-increasing application of nanosilver in consumer products, water disinfection and healthcare settings, have raised concerns over the public health/environmental safety of this nanomaterial. The current ubiquity of nanosilver may result in repeated exposure through various routes (skin, inhalation, or ingestion) which may lead to health complications. While there are a number of review articles and case studies published to date on the subject, an updated coherent review that clearly delineates thresholds and safe doses is lacking. Thus, it is plausible to have an overview of the most recent findings on the threshold limits, safe doses of silver and its related nanoscale forms, and the needed actions to ensure the safety and health of human, terrestrial and aquatic lives. This review provides an account of the effects of nanosilver in our daily lives. STATEMENT OF SIGNIFICANCE: This manuscripts is a review of the toxicity of nanosized silver. With respect to the existing literature, it goes beyond stating that there is a knowledge gap, drawing the attention of a wider readership to the ever-growing evidence of nanosilver toxicity to human and nature, and outlining the dose thresholds based on comprehensive data mining and visualisation. There are nearly 500 consumer products that claim to contain nanosilver. Thus, we trust a review of recent conclusive findings is timely. This manuscript is in line with the scope of the Journal, enabling a better understanding of the biological response to a widely-used bionanomaterial. Moreover, it provides a bigger picture of the link between surface properties and biocompatibility of nanosilver in different forms.
Background
The present study aimed to evaluate the potential differences in the biological effects of two types of spherical silver particles of 20 and 200 nm (Ag20 and Ag200), and of PVP-coated silver nanowires (AgNWs) with a diameter of 50 nm and length up to 50 μm, using a complex 3D model representative for the alveolar barrier cultured at air-liquid interface (ALI). The alveolar model was exposed to 0.05, 0.5 and 5 μg/cm² of test compounds at ALI using a state-of-the-art exposure system (Vitrocell™Cloud System). Endpoints related to the oxidative stress induction, anti-oxidant defence mechanisms, pro-inflammatory responses and cellular death were selected to evaluate the biocompatibility of silver particles and nanowires (AgNMs) and to further ascribe particular biological effects to the different morphologic properties between the three types of AgNMs evaluated.
Results
Significant cytotoxic effect was observed for all three types of AgNMs at the highest tested doses. The increased mRNA levels of the pro-apoptotic gene CASP7 suggests that apoptosis may occur after exposure to AgNWs. All three types of AgNMs increased the mRNA level of the anti-oxidant enzyme HMOX-1 and of the metal-binding anti-oxidant metallothioneins (MTs), with AgNWs being the most potent inducer. Even though all types of AgNMs induced the nuclear translocation of NF-kB, only AgNWs increased the mRNA level of pro-inflammatory mediators. The pro-inflammatory response elicited by AgNWs was further confirmed by the increased secretion of the 10 evaluated interleukins.
Conclusion
In the current study, we demonstrated that the direct exposure of a complex tetra-culture alveolar model to different types of AgNMs at ALI induces shape- and size-specific biological responses. From the three AgNMs tested, AgNWs were the most potent in inducing biological alterations. Starting from 50 ng/cm², a dose representative for an acute exposure in a high exposure occupational setting, AgNWs induced prominent changes indicative for a pro-inflammatory response. Even though the acute responses towards a dose representative for a full-lifetime exposure were also evaluated, chronic exposure scenarios at low dose are still unquestionably needed to reveal the human health impact of AgNMs during realistic conditions.
Electronic supplementary material
The online version of this article (10.1186/s12989-019-0297-1) contains supplementary material, which is available to authorized users.
The recent emergence of nanotechnology has provided a new therapeutic modality in case of silver nanoparticles. Dressings containing silver form the basis for the treatment of burns and wounds, either acute or chronic ones. The aim of the study was to examine silver release from the different wound dressings: commercially available (Atrauman Ag, Aquacel Ag) and experimental (FKDP-AgNPs) using micellar electrokinetic chromatography
(MEKC). In order to characterize prepared keratin based wound dressing before and after its modification with AgNPs, a compositional analysis was conducted using energy dispersive Xray (EDX) spectroscopy. Nanosilver toxicity was evaluated with the MTS test. Silver release from wound dressings was assessed using MEKC. The best separation was observed for MEKC in 20 mM borate buffer at pH 9.0 with 20 mM SDS addition. In vitro studies showed silver at higher concentration than 10 ppm exerted a toxic effect on fibroblasts isolated from diabetic mice vs. NIH/3T3 and BJ cell lines (p<0.05).
We observed silver was released more gradually from experimental FKDP-AgNPs wound dressing, in compare to commercially available wound dressings. The fast and low-cost method utilizing MEKC can be used in clinical practice to detect silver release from the
wound dressings.
To fabricate new smart materials that can deliver both the pharmaceutically active molecules and metal nanoparticles, we have formulated chitosan-based semi-IPN hydrogels and their silver nanocomposites (Ag NCs) along with amoxicillin (AMX). Semi-IPN hydrogels and their Ag NCs were synthesized from chitosan, dimethylamino ethyl methacrylate and 2-hydroxyethyl methacrylate via simple-free radical polymerization method and reducing with NaBH4. The resultant formulations were evaluated for in vitro release of AMX, anti-bacterial studies and DNA cleavage studies. The hydrogels with AMX-derived silver nanoparticles (Ag NPs) show better ability to cleave DNA and anti-microbial activity than individual AMX and Ag NPs.
Green alga, Rhizoclonium riparium was treated with silver nitrate solution (9 mM) for synthesis of biocompatible silver nanoparticle (SNP). After 72 h of reaction, the filaments of Rhizoclonium turned dark brown in color and initially synthesis of SNP was confirmed by observing absorption maxima at 415 nm in Uv-vis spectroscopy. The crystallographic nature and purity of particles were analysed by X-ray powder diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDAX) respectively. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of C-H, N-H, CC , CO functional groups on SNP surface. Recorded surface charge of SNP was-41.4 mV. Transmission Electron Microscopy (TEM) revealed that SNPs were spherical in nature with ~2-40 nm in size. The binding affinity between DNA and SNP was tested by agarose gel electrophoresis. TEM micrographs of SNP-DNA showed the particles arrangement in a series adjoining with each other. Algicidal activity of SNP against unicellular alga, Chlorococcum infusionum was confirmed by agar well diffusion method. Upregulation of stress enzymes such as catalase, super oxide dismutase and ascorbate peroxidase together with carotenoid content were recorded against Ag + stress. Extracted carotenoids, proteins and chloroplasts from Rhizoclonium also showed high efficiency in reduction of Ag + ions and subsequent production of SNP.
We report an effective method to produce surface-enhanced Raman scattering (SERS) substrates with improved enhancement efficiency, high uniformity, greater chemical and physical stability and absolute synthetic reproducibility. Nano bipyramidal (NBP) Au core and Ag shell nanorods (NRs) with variable length were prepared simply by varying the Ag precursor amount during growth and could successfully prepared NRs of length from 200 nm to 1200 nm and studied their formation mechanism and morphology using transmission electron microscopy (TEM) and optical properties by using UV-vis-NIR and Raman spectroscopy. Here we have utilized both the properties of Au and Ag nanoparticles by synthesizing Au@Ag core-shell NRs for high SERS enhancement. NRs have stronger absorption and large scattering cross-section for electromagnetic radiation and variation of aspect ratios of these NRs leads to a broad band surface plasmon tuning in the vis-NIR region. Relative SERS enhancement efficiency of these core-shell gold@silver NRs have been measured by using 4-mercaptobenzoic acid (4-MBA), crystal violet (CV) and 4-mercaptopyridine (4-MPy) as Raman tag and the obtained SERS results show their huge enhancement (~10¹⁰ for 4-MBA) which was substantiated through finite-difference time-domain (FDTD) computer simulations. Our work show superior SERS enhancement compared to the previously reported result for pure Au and Ag NRs and bimetallic nanorods with Au nanorod as core and Ag shell having aspect ratio in the same range.
This review is written with the goal of informing public health concerns related to nanoscience, while raising awareness of nanomaterials toxicity among scientists and manufacturers handling them. We show that humans have always been exposed to nanoparticles and dust from natural sources and human activities, the recent development of industry and combustion-based engine transportation profoundly increasing anthropogenic nanoparticulate pollution. The key to understanding the toxicity of nanoparticles is that their minute size, smaller than cells and cellular organelles, allows them to penetrate these basic biological structures, disrupting their normal function. Among diseases associated with nanoparticles are asthma, bronchitis, lung cancer, neurodegenerative diseases (such as Parkinson`s and Alzheimer`s diseases), Crohn`s disease, colon cancer. Nanoparticles that enter the circulatory system are related to occurrence of arteriosclerosis, and blood clots, arrhythmia, heart diseases, and ultimately cardiac death. We show that possible adverse effects of nanoparticles on human health depend on individual factors such as genetics and existing disease, as well as exposure, and nanoparticle chemistry, size, shape, and agglomeration state. The faster we will understand their causes and mechanisms, the more likely we are to find cures for diseases associated with nanoparticle exposure. We foresee a future with better-informed, and hopefully more cautious manipulation of engineered nanomaterials, as well as the development of laws and policies for safely managing all aspects of nanomaterial manufacturing, industrial and commercial use, and recycling.
Nanoparticles agglomerate and clump in solution, making it difficult to accurately deliver them for in vivo or in vitro experiments. Thus, experiments were conducted to determine the best method to suspend nanosized particles. Ultrafine and fine carbon black and titanium dioxide were suspended in phosphate buffered saline (PBS), rat and mouse bronchoalveolar lavage fluid (BALF), and PBS containing dipalmitoyl phosphatidylcholine (DPPC) and/or mouse serum albumin. To assess and compare how these various suspension media dispersed the nanoparticles, images were taken using light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results of this study show that PBS is not a satisfactory medium to prepare nanoparticle suspensions. However, BALF was an excellent media in which to suspend nanoparticles. The use of PBS containing protein or DPPC alone, in concentrations found in BALF, did not result in satisfactory particle dispersion. However, PBS-containing protein plus DPPC was satisfactory, although less effective than BALF.
Nanoscale zerovalent iron (NZVI) particles are 5–40nm sized Fe0/Fe-oxide particles that rapidly transform many environmental contaminants to benign products and are a promising in situ
remediation agent. Rapid aggregation and limited mobility in water-saturated porous media limits the ability to deliver NZVI
dispersions in the subsurface. This study prepares stable NZVI dispersions through physisorption of commercially available
anionic polyelectrolytes, characterizes the adsorbed polymer layer, and correlates the polymer coating properties with the
ability to prevent rapid aggregation and sedimentation of NZVI dispersions. Poly(styrene sulfonate) with molecular weights
of 70k and 1,000k g/mol (PSS70K and PSS1M), carboxymethyl cellulose with molecular weights of 90k and 700k g/mol (CMC90K
and CMC700K), and polyaspartate with molecular weights of 2.5k and 10k g/mol (PAP2.5K and 10K) were compared. Particle size
distributions were determined by dynamic light scattering during aggregation. The order of effectiveness to prevent rapid
aggregation and stabilize the dispersions was PSS70K(83%)>≈PAP10K(82%)>PAP2.5K(72%)>CMC700K(52%), where stability is
defined operationally as the volume percent of particles that do not aggregate after 1h. CMC90K and PSS1M could not stabilize
RNIP relative to bare RNIP. A similar trend was observed for their ability to prevent sedimentation, with 40, 34, 32, 20,
and 5wt%, of the PSS70K, PAP10K, PAP2.5K, CMC700K, and CMC90K modified NZVI remaining suspended after 7h of quiescent settling,
respectively. The stable fractions with respect to both aggregation and sedimentation correlate well with the adsorbed polyelectrolyte
mass and thickness of the adsorbed polyelectrolyte layers as determined by Oshima’s soft particle theory. A fraction of the
particles cannot be stabilized by any modifier and rapidly agglomerates to micron sized aggregates, as is also observed for
unmodified NZVI. This non-dispersible fraction is attributed to strong magnetic attractions among the larger particles present
in the polydisperse NZVI slurry, as the magnetic attractive forces increase as r6.
The increasing use of manufactured nanoparticles ensures these materials will make their way into the environment. Silver
nanoparticles in particular, due to use in a wide range of applications, have the potential to get into water systems, e.g.,
drinking water systems, ground water systems, estuaries, and/or lakes. One important question is what is the chemical and
physical state of these nanoparticles in water? Are they present as isolated particles, agglomerates or dissolved ions, as
this will dictate their fate and transport. Furthermore, does the chemical and physical state of the nanoparticles change
as a function of size or differ from micron-sized particles of similar composition? In this study, an electrospray atomizer
coupled to a scanning mobility particle sizer (ES-SMPS) is used to investigate the state of silver nanoparticles in water
and aqueous nitric acid environments. Over the range of pH values investigated, 0.5–6.5, silver nanoparticles with a bimodal
primary particle size distribution with the most intense peak at 5.0±7.4nm, as determined from transmission electron microscopy
(TEM), show distinct size distributions indicating agglomeration between pH 6.5 and 3 and isolated nanoparticles at pH values
from 2.5 to 1. At the lowest pH investigated, pH 0.5, there are no peaks detected by the SMPS, indicating complete nanoparticle
dissolution. Further analysis of the solution shows dissolved Ag ions at a pH of 0.5. Interestingly, silver nanoparticle dissolution
shows size dependent behavior as larger, micron-sized silver particles show no dissolution at this pH. Environmental implications
of these results are discussed.
KeywordsSilver nanoparticles-Agglomeration-Dissolution-Acidic environments-Environmental implications
Abstract Aggregation of metal oxide nanoparticles in aqueous media complicates interpretation of in vitro studies of nanoparticle-cell interactions. We used dynamic light scattering to investigate the aggregation dynamics of iron oxide and zinc oxide nanoparticles. Our results show that iron oxide particles aggregate more readily than zinc oxide particles. Pretreatment with serum stabilises iron oxide and zinc oxide nanoparticles against aggregation. Serum-treated iron oxide is stable only in pure water, while zinc oxide is stable in water or cell culture media. These findings, combined with zeta potential measurements and quantification of proteins adsorbed on particle surface, suggest that serum stabilisation of iron oxide particles occurs primarily through protein adsorption and resulting net surface charge. Zinc oxide stabilisation, however, also involves steric hindrance of particle aggregation. Fluid shear at levels used in flow experiments breaks up iron oxide particle aggregates. These results enhance our understanding of nanoparticle aggregation and its consequences for research on the biological effects of nanomaterials.
The dispersion stabilization of silver nanoparticles (AgNPs) in synthetic lung fluid was studied to interrogate the effects on colloidal stability due to the principal constituents of the fluid. The colloidal stability of 20 nm citrate-AgNPs dispersed in the presence of each constituent of the synthetic lung fluid (individually, the complete fluid, and without additives) was observed during titration of increasing sodium chloride concentration. A variety of complementary in situ measurement techniques were utilized, including dynamic light scattering, ultraviolet-visible absorption spectroscopy, atomic force microscopy, and small-angle X-ray scattering, which provided a collective set of information that enabled far better understanding of the dispersion behavior in the fluid than any one technique alone. It was observed that AgNPs continued to adsorb bovine serum albumin (BSA) protein from the synthetic lung fluid solution as the sodium chloride concentration increased, until a maximum BSA coating was achieved prior to reaching the physiological sodium chloride concentration of 154 mmol L(-1). BSA was determined to be the constituent of the synthetic lung fluid that is required to provide colloidal stability at high salt loadings, though the phospholipid constituent exerts a subtle effect. Additionally, as AgNPs are a distinctly different class of nanoparticles apart from the carbon nanotubes and titanium dioxide nanoparticles initially reported to be dispersible using this fluid, this work also demonstrates the broad applicability of synthetic lung fluid in providing stable dispersions for engineered nanoparticles for use in biological assays.
This review is presented as a common foundation for scientists interested in nanoparticles, their origin,activity, and biological toxicity. It is written with the goal of rationalizing and informing public health concerns related to this sometimes-strange new science of "nano," while raising awareness of nanomaterials' toxicity among scientists and manufacturers handling them.We show that humans have always been exposed to tiny particles via dust storms, volcanic ash, and other natural processes, and that our bodily systems are well adapted to protect us from these potentially harmful intruders. There ticuloendothelial system, in particular, actively neutralizes and eliminates foreign matter in the body,including viruses and nonbiological particles. Particles originating from human activities have existed for millennia, e.g., smoke from combustion and lint from garments, but the recent development of industry and combustion-based engine transportation has profoundly increased an thropogenic particulate pollution. Significantly, technological advancement has also changed the character of particulate pollution, increasing the proportion of nanometer-sized particles--"nanoparticles"--and expanding the variety of chemical compositions. Recent epidemiological studies have shown a strong correlation between particulate air pollution levels, respiratory and cardiovascular diseases, various cancers, and mortality. Adverse effects of nanoparticles on human health depend on individual factors such as genetics and existing disease, as well as exposure, and nanoparticle chemistry, size, shape,agglomeration state, and electromagnetic properties. Animal and human studies show that inhaled nanoparticles are less efficiently removed than larger particles by the macrophage clearance mechanisms in the lungs, causing lung damage, and that nanoparticles can translocate through the circulatory, lymphatic, and nervous systems to many tissues and organs, including the brain. The key to understanding the toxicity of nanoparticles is that their minute size, smaller than cells and cellular organelles, allows them to penetrate these basic biological structures, disrupting their normal function.Examples of toxic effects include tissue inflammation, and altered cellular redox balance toward oxidation, causing abnormal function or cell death. The manipulation of matter at the scale of atoms,"nanotechnology," is creating many new materials with characteristics not always easily predicted from current knowledge. Within the nearly limitless diversity of these materials, some happen to be toxic to biological systems, others are relatively benign, while others confer health benefits. Some of these materials have desirable characteristics for industrial applications, as nanostructured materials often exhibit beneficial properties, from UV absorbance in sunscreen to oil-less lubrication of motors.A rational science-based approach is needed to minimize harm caused by these materials, while supporting continued study and appropriate industrial development. As current knowledge of the toxicology of "bulk" materials may not suffice in reliably predicting toxic forms of nanoparticles,ongoing and expanded study of "nanotoxicity" will be necessary. For nanotechnologies with clearly associated health risks, intelligent design of materials and devices is needed to derive the benefits of these new technologies while limiting adverse health impacts. Human exposure to toxic nanoparticles can be reduced through identifying creation-exposure pathways of toxins, a study that may someday soon unravel the mysteries of diseases such as Parkinson's and Alzheimer's. Reduction in fossil fuel combustion would have a large impact on global human exposure to nanoparticles, as would limiting deforestation and desertification.While nanotoxicity is a relatively new concept to science, this review reveals the result of life's long history of evolution in the presence of nanoparticles, and how the human body, in particular, has adapted to defend itself against nanoparticulate intruders.
Inorganic colloidal nanoparticles are very small, nanoscale objects with inorganic cores that are dispersed in a solvent. Depending on the material they consist of, nanoparticles can possess a number of different properties such as high electron density and strong optical absorption (e.g. metal particles, in particular Au), photoluminescence in the form of fluorescence (semiconductor quantum dots, e.g. CdSe or CdTe) or phosphorescence (doped oxide materials, e.g. Y(2)O(3)), or magnetic moment (e.g. iron oxide or cobalt nanoparticles). Prerequisite for every possible application is the proper surface functionalization of such nanoparticles, which determines their interaction with the environment. These interactions ultimately affect the colloidal stability of the particles, and may yield to a controlled assembly or to the delivery of nanoparticles to a target, e.g. by appropriate functional molecules on the particle surface. This work aims to review different strategies of surface modification and functionalization of inorganic colloidal nanoparticles with a special focus on the material systems gold and semiconductor nanoparticles, such as CdSe/ZnS. However, the discussed strategies are often of general nature and apply in the same way to nanoparticles of other materials.
One of the most important functions of the lung surfactant monolayer is to form the first line of defence against inhaled aerosols such as nanoparticles (NPs), which remains largely unexplored. We report here, for the first time, the interaction of polyorganosiloxane NPs (AmorSil20: 22 nm in diameter) with lipid monolayers characteristic of alveolar surfactant. To enable a better understanding, the current knowledge about an established model surface film that mimics the surface properties of the lung is reviewed and major results originating from our group are summarized. The pure lipid components dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol have been used to study the biophysical behaviour of their monolayer films spread at the air-water interface in the presence of NPs. Film balance measurements combined with video-enhanced fluorescence microscopy have been used to investigate the formation of domain structures and the changes in the surface pattern induced by NPs. We are able to show that NPs are incorporated into lipid monolayers with a clear preference for defect structures at the fluid-crystalline interface leading to a considerable monolayer expansion and fluidization. NPs remain at the air-water interface probably by coating themselves with lipids in a self-assembly process, thereby exhibiting hydrophobic surface properties. We also show that the domain structure in lipid layers containing surfactant protein C, which is potentially responsible for the proper functioning of surfactant material, is considerably affected by NPs.
Nanoparticles are characterized by having a high surface area per mass. Particulate surface area has been reported to play an important role in determining the biological activity of nanoparticles. However, recent reports have questioned this relationship. This study was conducted to determine whether mass of particles or surface area of particles is the more appropriate dose metric for pulmonary toxicity studies. In this study, rats were exposed by intratracheal instillation to various doses of ultrafine and fine carbon black. At 1, 7, or 42 days post-exposure, inflammatory and cytotoxic potential of each particle type was compared on both a mass dosage (mg/rat) as well as an equal surface area dosage (cm2 of particles per cm2 of alveolar epithelium). In an additional study, the pulmonary responses to instillation of ultrafine carbon black were compared to equivalent particle surface area doses of ultrafine titanium dioxide.
Ultrafine carbon black particles caused a dose dependent but transient inflammatory and cytotoxic response. On a mass basis, these responses were significantly (65 fold) greater than those for fine sized carbon black. However, when doses were equalized based on surface area of particles given, the ultrafine carbon black particles were only slightly (non-significantly) more inflammogenic and cytotoxic compared to the fine sized carbon black. At one day post-exposure, inflammatory potencies of the ultrafine carbon black and ultrafine titanium dioxide particles were similar. However, while the pulmonary reaction to ultrafine carbon black resolved with time, the inflammatory effects of ultrafine titanium dioxide were more persistent over a 42 day post-exposure period.
These results indicate that for low toxicity low solubility materials, surface area of particles administered rather than mass burden of particles may be a more appropriate dose metric for pulmonary toxicity studies. In addition, ultrafine titanium dioxide appears to be more bioactive than ultrafine carbon black on an equivalent surface area of particles delivered basis.
Individuals with chronic lung disease are at increased risk of adverse health effects from airborne particulate matter. Characterization of underlying pollutant-phenotype interactions may require comprehensive strategies. Here, a toxicogenomic approach was used to investigate how inflammation modifies the pulmonary response to urban particulate matter.
Transgenic mice with constitutive pulmonary overexpression of tumour necrosis factor (TNF)-alpha under the control of the surfactant protein C promoter and wildtype littermates (C57BL/6 background) were exposed by inhalation for 4 h to particulate matter (0 or 42 mg/m3 EHC-6802) and euthanized 0 or 24 h post-exposure. The low alveolar dose of particles (16 mug) did not provoke an inflammatory response in the lungs of wildtype mice, nor exacerbate the chronic inflammation in TNF animals. Real-time PCR confirmed particle-dependent increases of CYP1A1 (30-100%), endothelin-1 (20-40%), and metallothionein-II (20-40%) mRNA in wildtype and TNF mice (p < 0.05), validating delivery of a biologically-effective dose. Despite detection of striking genotype-related differences, including activation of immune and inflammatory pathways consistent with the TNF-induced pathology, and time-related effects attributable to stress from nose-only exposure, microarray analysis failed to identify effects of the inhaled particles. Remarkably, the presence of chronic inflammation did not measurably amplify the transcriptional response to particulate matter.
Our data support the hypothesis that health effects of acute exposure to urban particles are dominated by activation of specific physiological response cascades rather than widespread changes in gene expression.
: The rapid emergence of nanotechnology including production of engineered nanoparticles is likely to provide our society with a continuous range of consumer products with advanced technology applications. Among the 580 consumer products containing known nanomaterials, the most common material is silver-based nanoparticles. Human exposure likelihood and needed risk exposure analysis to these product-derived nanomaterials are now required for every age level. Further, disposal and degradation of these products and release from engineered sources has an indirect human exposure potential and an environmental impact concern. The approach to assess toxicity of nanomaterials is a new and evolving field. Most nanotoxicology studies have focused on mechanistic understanding using in vitro models with the early reports demonstrating that high levels of silver nanoparticles are lethal to eukaryotic cell-based systems. Nanotoxicology assessment studies performed in vivo using appropriate dosing amounts and routes of exposure carry greater significance because of the diversity of systemic phenotypic response and the physiologic/anatomic influence that can be translatable from animal models to human exposures. Particle pharmacokinetics and dynamics of nondissolved solution materials combined with issues of regional dissolution rates can provide the true impact of dosing on systemic physiology and positional anatomy. The present information on silver nanoparticle toxicity in vivo has been limited. More importantly, there remains a need to differentiate between soluble/ionic forms of silver in tissues or a test for the presence of insoluble salts. Thus the distribution of silver nanoparticle after inhalation will require much more information to delineate distribution kinetics/dynamics, toxicity processes, and define key mechanisms for the effects observed.
Nanotechnology is a relatively new discipline which is growing rapidly and is used in a broad-spectrum of applications such as engineering, medicine, cosmetics, sports goods and textiles. The number of consumer products that employ nanotechnology is steadily increasing. Nanomaterials have novel and diverse properties very different to those of the same materials on a macroscopic scale, exhibiting unique optical, electronic and magnetic properties. Not surprising then that these engineered materials are being used to create new products and applications, and to improve existing products.
Integrating basic and clinical research on the biophysical and physiological functions of pulmonary surfactants, this practical reference presents thorough, cutting-edge coverage on surfactant-related lung disease. Manage neonatal respiratory distress syndrome (RDS), acute respiratory distress syndrome (ARDS), and acute lung injury more effectively!
The protein-nanoparticle (NP) interface is a current frontier of multiple disciplines, full of challenges and opportunities. The unique behaviors of nanomaterials (NMs) bring many exciting applications, and also raise safety concerns. Beyond bioapplications, various NMs could also enter human bodies from the environment. When entering human bodies, NPs interact with various biomolecules, especially proteins, forming a protein corona. This protein-NP complex is what the biosystems 'see' and 'respond to'. Therefore, understanding how NPs interact with proteins is crucial for both bioapplications and the biosafety of NMs. In this review, the current understanding of protein-NP interactions is summarized, including the theoretical background, experimental results, and computational progresses. Guidelines for improving bioapplication performance and reducing the potential biosafety hazard of NMs by designing the protein-NP interactions are discussed, along with future directions and challenges in this exciting field.
Our laboratory has reported that rat bronchoalveolar lavage (BAL) fluid is an effective nanoparticle (NP) dispersant. However, its utility is constrained by its cost and the lack of standardization to control for intra- and inter-laboratory variability in BAL fluid. In this study, we report the efficacy and biocompatibility of a dispersion medium (DM), which is a ‘lung fluid mimic’. In vitro studies, which used dynamic light scattering and transmission electron microscopy, determined that ultrafine titanium dioxide and ultrafine carbon black are equally well dispersed by DM or BAL fluid. We also determined that DM was effective at dispersing multi-walled carbon nanotubes. In vivo, when used as a vehicle, DM per se did not elicit toxicity and did not influence or alter toxic responses to crystalline silica in either the lung or brain. Overall, these studies indicate that DM is an effective, biocompatible, and economical vehicle for nanotoxicological studies.
The study of the interaction between Langmuir monolayers of 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), as the major component of lung surfactant (LS), and nanoparticles of different nature, hydrophilic silica (SiO2) and hydrophobic carbon black (CB), has been carried out by measuring the compression Π–A isotherms and the response of the surface pressure to harmonic variations of the interfacial area simulating respiratory cycles in a Langmuir trough. The change of the monolayer interfacial structure induced by nanoparticles was monitored by Brewster angle microscopy. The results point out that nanoparticles incorporating into the monolayers influence the interfacial organization of the molecules and induce important modifications in both the phase behavior and the mechanical properties. Silica has stronger effects on DPPC phase behavior, compared to carbon black, while both affect the monolayer elasticity, the collapse conditions, and the nonlinearity of the surface pressure response to area expansion–compression simulating the respiratory cycles. With DPPC being the major component of pulmonary surfactant, the results here obtained are relevant in the framework of wider studies on the effect of nanoparticles on the pulmonary surfactant interfacial properties.
The brightness and efficiency of liquid crystal displays can be improved by replacing the second polarizer and color filter with a single oriented polyethylene film containing monodisperse silver nanoparticles, as revealed in the Figure. The preparation of the films, which exhibit bright colors and appear yellow or red (see cover), depending on the polarization direction of the incident light, is described.
Spherical silver nanoparticles were grown in situ in different polyamides by a thermal reduction of silver acetate during
melt processing of the polymers. Most of the particles have a diameter of about 20nm. The absolute amount as well as the
kinetics of the silver ion release from the various polyamide/silver nanocomposites differ strongly, although the filler content
in all materials is the same (1.5wt. %) and the morphologies of the silver particles are not very different. One result of
the investigations was that the absolute amount of the long-term silver ion release increases exponentially with the maximum
water absorption of the polymers used as matrix materials, because silver ions are formed from elemental silver particles
in the presence of water, only. Moreover, it was also found that the long-term silver ion release increases with a growing
diffusion coefficient of water in the polymer. The water absorption properties of the polymers govern the kinetics of the
silver ion release, too: for strong hydrophilic polyamides like PA6 or PA6.6, which are plasticized by water, the silver ion
release is a zero-order process. For nanocomposites with less hydrophilic polyamides like a cycloaliphatic polyamide or a
P12 modified with polytetrahydrofurane (PA12-poly-THF), the silver ion release is governed by diffusion. As expected from
the efficacy of the silver ion release, PA6, PA6.6, PA12 and PA12 modified with polytetrahydrofurane and a cycloaliphatic
polyamide filled with 1.5wt. % of silver nanoparticles are active against Escherichia coli. But, only nanocomposites with PA6, PA6.6 and P12-poly-THF as matrix materials are suitable as long-term biocidal materials.
Nanoparticles, the building blocks of many engineered nanomaterials, can make their way into the environment or into organisms,
either accidentally or purposefully. The intent of this study is to provide some insight into the complex environmental, health,
and safety issues associated with engineered nanomaterials. In particular, here the state of commercially manufactured silver
nanoparticles—i.e., will silver nanoparticles be present as isolated particles, agglomerates, or dissolved ions—in two simulated
biological media is explored. Two different commercially manufactured silver nanoparticle samples, one that has been surface
modified with a thick polymer coating to render them more water-soluble and the other, with a sub-nanometer surface layer,
are studied. The experimental results and the extended DLVO model calculations show that silver nanoparticles have a propensity
to settle out in high ionic strength media independent of surface modification. Furthermore, single nanoparticles as well
as aggregates/agglomerates are present together in these solutions. Silver ion release in these simulated biological buffers
with pHs of 4.5 and 7.4 is negligible after 96h.
KeywordsSilver nanoparticles–Agglomeration–Dissolution–Sedimentation–Artificial biological fluids–Health and safety
The changes in electrokinetic properties of silica suspensions in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospshocholine (DPPC) were investigated via zeta potential, mean diameter and transmittance determinations. Silica
particles were precovered with monolayer (ML) or bilayer (BL) of the phospholopid from chloroform solution (SiO2/DPPC) or covered by DPPC adsorption from aqueous solution (SiO2+DPPC). The zeta potential and mean diameter of SiO2/DPPC suspension were measured as a function of NaCl concentration and due to the phospholipase A2(PLA2) action in 10−3M NaCl solution and buffer Tris at pH=8 and9. It was found that the DPPC adsorption onto silica surface decreases its the
zeta potential, however the suspensions were stable during the experiment time, probably because of steric stabilization.
During PLA2 enzyme action the changes in zeta potential were observed, which were caused by the hydrolysis products, especially palmitic
acid molecules, which also had influence on the stability of these systems.
KeywordsDPPC-Silica-Phospholipase A2
-Zeta potential-Transmittance-Particle size-Stability
Synthetic aspects of silver nanoparticle preparation in one-and two-phase aqueous and water-organic media and the influence
of experimental factors on particle size and surface hydrophilicity/hydrophobicity are studied. It is shown that silver nanoparticles
with controlled mean size and surface hydrophilic-hydrophobic properties can be obtained through direct synthesis or successive
transformations.
We report the complete assignment of the vibrational spectrum of dipalmitoylphosphatidylcholine (DPPC), which belongs to the most ubiquitous membrane phospholipid family, phosphatidylcholine. We find that water hydrating the lipid headgroups enables efficient energy transfer across membrane leaflets on sub-picosecond time scales. The emergence of spatially extended vibrational modes upon hydration, underlies this phenomenon. Our findings illustrate the importance of collective molecular behavior of biomembranes and reveal that hydrated lipid membranes can act as efficient media for the transfer of vibrational energy.
Fluorescence correlation spectroscopy (FCS) was used to determine diffusion coefficients (D) of the Suwannee River fulvic and humic acids (SRFA and SRHA) and to measure the effects of pH, ionic strength, Ca, and humic substance (HS) concentration on the value of D. For these HS, average diffusion coefficients were in the range of (2-3) x 10(-10) m(2) s(-1) (corresponding to hydrodynamic diameters of approximately 1.5-2.1 nm). Small, but significant, decreases in the diffusion coefficients were observed with decreasing pH, most likely indicating that a small degree of aggregation (formation of dimers and trimers) was occurring. The effect of ionic strength (up to 100 mM) was either small or insignificant, but, where a change occurred, there was a tendency toward a reduction in the diffusion coefficient with increasing sa It concentration. No effect of HS concentration (1-50 mg L(-1)) or hydration time (1-14 days) was observed. There were no observable effects of Ca in comparison to Na, at an ionic strength of 5 mM. For all conditions studied, SRFA had a higher diffusion coefficient than SRHA which is in agreement with literature data on their respective molar masses. Since this is the first application of FCS to HS, the technique was systematically tested for artifacts, in particular photobleaching and the effect of fluorescence excitation wavelength. Despite a small amount of photobleaching due to the intense laser excitation, FCS was found to be suitable for use with fulvic or humic acids.
A simple approach to decorate carbon nanotube (CNT) with silver nanoparticles (Ag-NPs) was developed to enhance the electrical conductivity of CNT. CNTs were functionalized using ball milling in the presence of ammonium bicarbonate, followed by reduction of silver ions in N, N-dimethylformamide, producing silver decorated CNTs (Ag@CNTs). The Ag@CNTs were employed as conducting filler in epoxy resin to fabricate electrically conducting polymer composites. The electrical, thermal and mechanical properties of the composites were measured and compared with those containing pristine and functionalized CNTs. It was found that when pH was about six, highly dispersed Ag-NPs can be decorated on functionalized CNTs. The electrical conductivity of composites containing 0.10 wt% of Ag@CNTs was more than four orders of magnitude higher than those containing same content of pristine and functionalized CNTs, confirming the advantage of the Ag@CNTs as effective conducting filler. The ameliorating effect of improved electrical conductivity was not at the expense of thermal or mechanical properties.
Charged lipids constitute a substantial fraction of all membrane lipids. Their charges vary in quantity and distribution within their headgroup regions. In long range interactions, their charges’ value and electrostatic potential in the vicinity of the membrane surface can be approximated by the Guy–Chapman theory. This theory treats the interface as a charged structureless plain surrounded by uniform environments. However, if one considers intermolecular interactions, such assumptions need to be revised. The interface is in reality a thick region containing the residual charges of lipid headgroups. Their arrangement depends on the type of lipid present in the membrane. The variety of lipids and their biological functions suggests that charge distribution determines the extent and type of interaction with surface associated molecules. Numerous examples show that protein behavior at the lipid bilayer surface is determined by the type of lipid present, indicating protein specificity towards certain surface locations and local properties (determined by lipid composition) of a particular type. Such specificity is achieved by a combination of electrostatic, hydrophobic and enthropic effects. Comparing lipid biological activity, it can be stated that residual charge distribution is one of the factors of intermolecular recognition leading to the specific interaction of lipid molecules and selected proteins in various processes, particularly those involved with signal transduction pathways. Such specificity enables a variety of processes occurring simultaneously on the same membrane surface to function without cross-reaction interference.
We investigate the structure and electronic properties of phosphatidylcholine (PC) under different degrees of hydration at the single-molecule and monolayer type level by linear scaling ab initio calculations. Upon hydration, the phospholipid undergoes drastic long-range conformational rearrangements which lead to a sickle-like ground-state shape. The structural unit of the tilted gel-phase PC appears to be a water-bridged PC dimer. We find that hydration dramatically alters the surface potential, dipole and quadrupole moments of the lipids and consequently guides the interactions of the lipids with other molecules and the communication between cells.
Aggregation, an important environmental behavior of silver nanoparticles (AgNPs) influences their bioavailability and cytotoxicity. The work studied the influence of dissolved oxygen (DO) or the redox potential on the stability of AgNPs in aqueous environments. This study employed time-resolved dynamic light scattering (TR-DLS) to investigate the aggregation kinetics of citrate-coated AgNPs. Our results demonstrated that when DO was present, the aggregation rates became much faster (e.g., 3-8 times) than those without DO. The hydrodynamic sizes of AgNPs had a linear growth within the initial 4-6 h and after the linear growth, the hydrodynamic sizes became random for AgNPs in the presence of DO, whereas in the absence of DO the hydrodynamic sizes grew smoothly and steadily. Furthermore, the effects of primary particles sizes (20, 40, and 80 nm) and initial concentrations (300 and 600 μg/L) of AgNPs on aggregation kinetics were also investigated.
Despite the increasing use of silver nanoparticles (Ag-NPs) in nanotechnology and their toxicity to invertebrates, the transformations and fate of Ag-NPs in the environment are poorly understood. This work focuses on the sulfidation processes of PVP-coated Ag-NPs, one of the most likely corrosion phenomena that may happen in the environment. The sulfur to Ag-NPs ratio was varied in order to control the extent of Ag-NPs transformation to silver sulfide (Ag₂S). A combination of synchrotron-based X-ray Diffraction (XRD) and Extended X-ray Absorption Fine Structure spectroscopy shows the increasing formation of Ag₂S with an increasing sulfur to Ag-NPs ratio. TEM observations show that Ag₂S forms nanobridges between the Ag-NPs leading to chain-like structures. In addition, sulfidation strongly affects surface properties of the Ag-NPs in terms of surface charge and dissolution rate. Both may affect the reactivity, transport, and toxicity of Ag-NPs in soils. In particular, the decrease of dissolution rate as a function of sulfide exposure may strongly limit Ag-NPs toxicity since released Ag⁺ ions are known to be a major factor in the toxicity of Ag-NPs.
The rapid development of nanotechnology and the related production and application of nanosized materials such as engineered nanoparticles (ENP) inevitably lead to the emission of these products into environmental systems. So far, little is known about the occurrence and the behaviour of ENP in environmental aquatic systems. In this contribution, the influence of natural organic matter (NOM) and ionic strength on the stability and the interactions of silver nanoparticles (n-Ag) in aqueous suspensions was investigated using UV-vis spectroscopy and asymmetrical flow field-flow fractionation (AF⁴) coupled with UV-vis detection and mass spectrometry (ICP-MS). n-Ag particles were synthesized by chemical reduction of AgNO₃ with NaBH₄ in the liquid phase at different NOM concentrations. It could be observed that the destabilization effect of increasing ionic strength on n-Ag suspensions was significantly decreased in the presence of NOM, leading to a more stable n-Ag particle suspension. The results indicate that this behaviour is due to the adsorption of NOM molecules onto the surface of n-Ag particles ("coating") and the resulting steric stabilization of the particle suspension. The application of AF⁴ coupled with highly sensitive detectors turned out to be a powerful method to follow the aggregation of n-Ag particle suspensions at different physical-chemical conditions and to get meaningful information on their chemical composition and particle size distributions. The method described will also open the door to obtain reliable data on the occurrence and the behaviour of other ENP in environmental aquatic systems.
The immune-response of macrophages is an important area of investigation since it represents the major pathway by which early-stage defense barriers are established in skin, lungs, and mucosal systems to counteract foreign objects. In this study, we have examined the size-dependent inflammatory and toxicological effects of nanostructured silver particles (nano-Ag) on macrophage immune cells.
Silver nanoparticles (AgNPs) are increasingly used as antimicrobial additives in consumer products and may have adverse impacts on organisms when they inadvertently enter ecosystems. This study investigated the uptake and toxicity of AgNPs to the common grass, Lolium multiflorum. We found that root and shoot Ag content increased with increasing AgNP exposures. AgNPs inhibited seedling growth. While exposed to 40 mg L(-1) GA-coated AgNPs, seedlings failed to develop root hairs, had highly vacuolated and collapsed cortical cells and broken epidermis and rootcap. In contrast, seedlings exposed to identical concentrations of AgNO(3) or supernatants of ultracentrifuged AgNP solutions showed no such abnormalities. AgNP toxicity was influenced by total NP surface area with smaller AgNPs (6 nm) more strongly affecting growth than did similar concentrations of larger (25 nm) NPs for a given mass. Cysteine (which binds Ag(+)) mitigated the effects of AgNO(3) but did not reduce the toxicity of AgNP treatments. X-ray spectro-microscopy documented silver speciation within exposed roots and suggested that silver is oxidized within plant tissues. Collectively, this study suggests that growth inhibition and cell damage can be directly attributed either to the nanoparticles themselves or to the ability of AgNPs to deliver dissolved Ag to critical biotic receptors.
As a result of the extensive number of applications of silver nanoparticles (AgNPs), their potential impacts, once released into the environment, are of concern. The toxicity of AgNPs was reported to be dependent on various factors such as particle size, shape and capping agent. Although these factors may play a role in AgNPs toxicity, the results presented herein suggest that surface charge is one of the most important factors that govern the toxicity of AgNPs. In the current study, the toxicity of four AgNPs representing various surface charging scenarios ranging from highly negative to highly positive was investigated. These AgNPs were (1) uncoated H(2)-AgNPs, (2) citrate coated AgNPs (Citrate-AgNPs), (3) polyvinylpyrrolidone coated AgNPs (PVP-AgNPs), and (4) branched polyethyleneimine coated AgNPs (BPEI-AgNPs). Our results clearly demonstrate that the AgNPs exhibited surface charge-dependent toxicity on the bacillus species investigated. Furthermore, ultrafiltration membranes were utilized to purify the AgNPs suspensions from residual impurities prior to the introduction to the microbes. This step was crucial in determining the true AgNPs toxicity and is either missing or not explicitly mentioned in most of the reported toxicity studies.
High-aspect ratio ZnO nanowires have become one of the most promising products in the nanosciences within the past few years with a multitude of applications at the interface of optics and electronics. The interaction of zinc with cells and organisms is complex, with both deficiency and excess causing severe effects. The emerging significance of zinc for many cellular processes makes it imperative to investigate the biological safety of ZnO nanowires in order to guarantee their safe economic exploitation. In this study, ZnO nanowires were found to be toxic to human monocyte macrophages (HMMs) at similar concentrations as ZnCl(2). Confocal microscopy on live cells confirmed a rise in intracellular Zn(2+) concentrations prior to cell death. In vitro, ZnO nanowires dissolved very rapidly in a simulated body fluid of lysosomal pH, whereas they were comparatively stable at extracellular pH. Bright-field transmission electron microscopy (TEM) showed a rapid macrophage uptake of ZnO nanowire aggregates by phagocytosis. Nanowire dissolution occurred within membrane-bound compartments, triggered by the acidic pH of the lysosomes. ZnO nanowire dissolution was confirmed by scanning electron microscopy/energy-dispersive X-ray spectrometry. Deposition of electron-dense material throughout the ZnO nanowire structures observed by TEM could indicate adsorption of cellular components onto the wires or localized zinc-induced protein precipitation. Our study demonstrates that ZnO nanowire toxicity in HMMs is due to pH-triggered, intracellular release of ionic Zn(2+) rather than the high-aspect nature of the wires. Cell death had features of necrosis as well as apoptosis, with mitochondria displaying severe structural changes. The implications of these findings for the application of ZnO nanowires are discussed.
Although silver nanoparticles are being exploited widely in antimicrobial applications, the mechanisms underlying silver nanoparticle antimicrobial properties in environmentally relevant media are not fully understood. The latter point is critical for understanding potential environmental impacts of silver nanoparticles. The aim of this study was to elucidate the influence of inorganic aquatic chemistry on silver nanoparticle stability (aggregation, dissolution, reprecipitation) and bacterial viability. A synthetic "fresh water" matrix was prepared comprising various combinations of cations and anions while maintaining a fixed ionic strength. Aggregation and dissolution of silver nanoparticles was influenced by electrolyte composition; experimentally determined ionic silver concentrations were about half that predicted from a thermodynamic model and about 1000 times lower than the maximum dispersed silver nanoparticle concentration. Antibacterial activity of silver nanoparticles was much lower than Ag(+) ions when compared on the basis of total mass added; however, the actual concentrations of dissolved silver were the same regardless of how silver was introduced. Bacterial inactivation also depended on bacteria cell type (Gram-positive/negative) as well as the hardness and alkalinity of the suspending media. These simple, but systematic studies--enabled by high-throughput screening--reveal the inherent complexity associated with understanding silver nanoparticle antibacterial efficacy as well as potential environmental impacts of silver nanoparticles.
Silver particles are used in various consumer products due to their positive effects, which include sterilization and antibacterial properties. However, it has been reported that silver nanoparticles (AgNPs) have strongly acute toxic effects on various cells. Therefore, the cytotoxicity of AgNPs was investigated, using Escherichia coli as a model organism, from the standpoint of three key metrics (ionic ratio, size, and agglomeration) that are the most relevant physicochemical properties. The findings indicated that cytotoxicity is depressed by the agglomeration of AgNPs. The order of toxic sensitivity was as follows: total Ag concentration > ionic ratio > size, the order of which was inversely related to the extent of agglomeration.
In recent decades, advances in nanotechnology engineering have given rise to the rapid development of many novel applications in the biomedical field. However, studies into the health and safety of these nanomaterials are still lacking. The main concerns are the adverse effects to health caused by acute or chronic exposure to nanoparticles (NPs), especially in the workplace environment. The lung is one of the main routes of entry for NPs into the body and, hence, a likely site for accumulation of NPs. Once NPs enter the interstitial air spaces and are quickly taken up by alveolar cells, they are likely to induce toxic effects. In this review, we highlight the different aspects of lung toxicity resulting from NP exposure, such as generation of oxidative stress, DNA damage and inflammation leading to fibrosis and pneumoconiosis, and the underlying mechanisms causing pulmonary toxicity.
The ever-increasing use of engineered nanomaterials will lead to heightened levels of these materials in the environment. The present review aims to provide a comprehensive overview of current knowledge regarding nanoparticle transport and aggregation in aquatic environments. Nanoparticle aggregation and deposition behavior will dictate particle transport potential and thus the environmental fate and potential ecotoxicological impacts of these materials. In this review, colloidal forces governing nanoparticle deposition and aggregation are outlined. Essential equations used to assess particle-particle and particle-surface interactions, along with Hamaker constants for specific nanoparticles and the attributes exclusive to nanoscale particle interactions, are described. Theoretical and experimental approaches for evaluating nanoparticle aggregation and deposition are presented, and the major findings of laboratory studies examining these processes are also summarized. Finally, we describe some of the challenges encountered when attempting to quantify the transport of nanoparticles in aquatic environments.
Many important aspects of nanosilver behavior are influenced by the ionic activity associated with the particle suspension, including antibacterial potency, eukaryotic toxicity, environmental release, and particle persistence.The present study synthesizes pure, ion-free, citrate-stabilized nanosilver (nAg) colloids as model systems, and measures their time-dependent release of dissolved silver using centrifugal ultrafiltration and atomic absorption spectroscopy. Ion release is shown to be a cooperative oxidation process requiring both dissolved dioxygen and protons. It produces peroxide intermediates, and proceeds to complete reactive dissolution under some conditions. Ion release rates increase with temperature in the range 0-37 °C, and decrease with increasing pH or addition of humic or fulvic acids. Sea salts have only a minor effect on dissolved silver release. Silver nanoparticle surfaces can adsorb Ag(+), so even simple colloids contain three forms of silver: Ag(0) solids, free Ag(+) or its complexes, and surface-adsorbed Ag(+). Both thermodynamic analysis and kinetic measurements indicate that Ag(0) nanoparticles will not be persistent in realistic environmental compartments containing dissolved oxygen. An empirical kinetic law is proposed that reproduces the observed effects of dissolution time, pH, humic/fulvic acid content, and temperature observed here in the low range of nanosilver concentration most relevant for the environment.
Viscometry was used to evaluate the effects of pH and supporting electrolyte concentration on the intrinsic viscosities of eight humic acids and one fulvic acid. Two synthetic poly(acrylic acid) (PAA) samples of different molecular weight were also studied for comparison. Humic and fulvic acid molecules behave as flexible entities that can swell or shrink in response to changes in pH and ionic strength. An increase in the solution pH leads to the development of negative charges in the molecules with the consequent electrostatic repulsion between ionized groups and molecular swelling. Increasing the ionic strength increases the screening of charges and leads to molecular shrinkage. The pH dependence decreases with increasing electrolyte concentration and at 10−1 M electrolyte the intrinsic viscosity is almost pH independent. The general behavior of PAAs is similar to that of the humics, though the effects of pH and electrolyte concentration are much larger for the PAAs. The degree of hydration of the humics differs for different samples. There are compact samples with low water content and swelling properties whereas other humics are more hydrated and flexible. All the studied humics have an internal structure that limits the expansion of the molecules when the electrolyte concentration is decreased. The latter is in accordance with the low values of the Mark–Houwink coefficient, α, of humics.
The extensive use of titanium dioxide nanoparticles (nano-TiO2) in many consumer products has raised concerns about possible risks to the environment The magnitude of the threat may depend on whether nano-TiO2 remains dispersed in the environment, or forms much larger-sized aggregates or clusters. Currently, limited information is available on the issue. In this context, the purpose of the present article is to report initial measurements of the morphology and rate of formation of nano-TiO2 aggregates in aqueous suspensions as a function of ionic strength and of the nature of the electrolyte in a moderately acid to circumneutral pH range typical of soil and surface water conditions. Dynamic light scattering results show that 4-5 nm titanium dioxide particles readily form stable aggregates with an average diameter of 50-60 nm at pH approximately 4.5 in a NaCl suspension adjusted to an ionic strength of 0.0045 M. Holding the pH constant but increasing the ionic strength to 0.0165 M, leads to the formation of micron-sized aggregates within 15 min. At all other pH values tested (5.8-8.2), micron-sized aggregates form in less than 5 min (minimum detection time), even at low ionic strength (0.0084-0.0099 M with NaCl). In contrast, micron-sized aggregates form within 5 min in an aqueous suspension of CaCl2 at an ionic strength of 0.0128 M and pH of 4.8, which is significantly faster than observed for NaCI suspensions with similar ionic strength and pH. This result indicates that divalent cations may enhance aggregation of nano-TiO2 in soils and surface waters. Optical micrographs show branching aggregates of sizes ranging from the 1 microm optical limit of the microscope to tens of micrometers in diameter.
Silver nanoparticles (Ag-np) are being used increasingly in wound dressings, catheters, and various household products due to their antimicrobial activity. The toxicity of starch-coated silver nanoparticles was studied using normal human lung fibroblast cells (IMR-90) and human glioblastoma cells (U251). The toxicity was evaluated using changes in cell morphology, cell viability, metabolic activity, and oxidative stress. Ag-np reduced ATP content of the cell caused damage to mitochondria and increased production of reactive oxygen species (ROS) in a dose-dependent manner. DNA damage, as measured by single cell gel electrophoresis (SCGE) and cytokinesis blocked micronucleus assay (CBMN), was also dose-dependent and more prominent in the cancer cells. The nanoparticle treatment caused cell cycle arrest in G(2)/M phase possibly due to repair of damaged DNA. Annexin-V propidium iodide (PI) staining showed no massive apoptosis or necrosis. The transmission electron microscopic (TEM) analysis indicated the presence of Ag-np inside the mitochondria and nucleus, implicating their direct involvement in the mitochondrial toxicity and DNA damage. A possible mechanism of toxicity is proposed which involves disruption of the mitochondrial respiratory chain by Ag-np leading to production of ROS and interruption of ATP synthesis, which in turn cause DNA damage. It is anticipated that DNA damage is augmented by deposition, followed by interactions of Ag-np to the DNA leading to cell cycle arrest in the G(2)/M phase. The higher sensitivity of U251 cells and their arrest in G(2)/M phase could be explored further for evaluating the potential use of Ag-np in cancer therapy.
Silver ions have been widely used as disinfectants that inhibit bacterial growth by inhibiting the essential enzymatic functions of the microorganism via interaction with the thiol-group of l-cysteine. However, silver-ion-mediated perturbation of the bacterial respiratory chain has raised the possibility of reactive oxygen species (ROS) generation. We used bacterial reporter strains specifically responding to superoxide radicals and found that silver-ion-mediated ROS-generation affected bactericidal activity. Almost half the log reduction in Escherichia coli and Staphylococcus aureus populations (model strains for gram negative and positive bacteria, respectively) caused by silver-ion disinfection was attributed to ROS-mediated bactericidal activity. The major form of ROS generated was the superoxide-radical; H(2)O(2) was not induced. Furthermore, silver ions strongly enhanced paraquat-induced oxidative stress, indicating close correlation and synergism between the conventional and ROS-mediated silver toxicity. Our results suggest that further studies in silver-based disinfection systems should consider the oxygen concentration and ROS reaction.
The nonspecific adsorption of charged nanoparticles onto single-component phospholipid bilayers bearing phosphocholine headgroups is shown, from fluorescence and calorimetry experiments, to cause surface reconstruction at the points where nanoparticles adsorb. Nanoparticles of negative charge induce local gelation in otherwise fluid bilayers; nanoparticles of positive charge induce otherwise gelled membranes to fluidize locally. Through this mechanism, the phase state deviates from the nominal phase transition temperature by tens of degrees. This work generalizes the notions of environmentally induced surface reconstruction, prominent in metals and semiconductors. Bearing in mind that chemical composition in these single-component lipid bilayers is the same everywhere, this offers a mechanism to generate patchy functional properties in phospholipid membranes.
• fluorescence
• adsorption
• phase transition
Dipalmitoyl phosphatidylcholine is the principal component of lung surfactant, and knowledge of its behavior as a film spread at the air-water interface is essential for understanding how lung surfactant itself works. We therefore studied the collapse rates of very low surface tension air-water monolayers of dipalmitoyl, dimyristoyl, and palmitoyl-myristoyl phosphatidylcholines at different temperatures. In each case we found that the monolayers abruptly became unstable at temperature 3-4 degree C above their bulk lipid-water phase transition temperatures (Tc). This accords with a comparable increase in Tc occurring in bulk systems subjected to high pressure. These findings are also consistent with the behavior of isolated rat lungs, which have been found to require higher transmural pressures to maintain a given volume on deflation when kept at temperature above the Tc of dipalmitoyl phosphatidylcholine.