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Nanosilver and its Medical Implications
... In the modern era of nanotechnology, there is a trend of using of Nano-silver impregnated dressings with the base of foam, hydrocolloid gel, gauze or film. U.S. Food and Drug Administration (FDA) have cleared many of such nanosilver impregnated dressings [42]. The nano-silver ladden dressing change colour when the antibiotic is released. ...
... With the advent of such system, there can be a reduction in antibiotic resistance. Silver nanoparticles impregnated ointment healed the wound in 3 days in contrast to any normal ointment (control), that took 7 days to heal [39,42]. Nano-silver is used in bone cements that are used as artificial joint replacements. ...
Nano-silver has already been clinically explored in ancient medicine i.e ayurveda in the form of Raupya bhasma/rajat bhasma. The resurgence of nano-silver has revolutionized not only as upcoming drug against anti-microbial drug resistant nosocomial infections , but has also evolved in diagnostics, targeted drug delivery, nano-implants, nano-fillers in dentistry, nano-cement in bones and as antiseptic and disinfectants. Several clinical trials have demonstrated their promise in bio-medical field for above mentioned areas. The only limitation observed in studies is its cumulative potential resulting in toxicity of silver known as argyria i.e grey black discolouration of skin. Moreover few studies have proved the presence of small quantities of heavy metals e.g mercury, arsenic, lead etc in ayurvedic formulations. Therefore, more toxicity studies are required to establish the safety and efficacy of nano-silver. Once toxic profile of nano-silver is established, it would be easy to apply uses of nano-silver firmly in various clinical aspects in medicine.
... Other advantages are the reduction of energy consumption, availability of various arrays as a biological resource, and stability and production of water-soluble nanoparticles (Khatoon et al. 2017;Mouxing et al. 2006;Müller et al. 2016;Shahverdi et al. 2007). On the other hand, poor understanding of the exact mechanism of nanoparticle production, controlling their size and shape, aggregation, and adhesion of nanoparticles are among the disadvantages of this production method (Ge et al. 2014;Mishra and Chauhan 2015). Bacterial synthesis of nanoparticles is produced either extracellularly or intracellularly. ...
The Ag/AgCl composite can be synthesized using various chemical, physical, and biological methods. Biosynthesis of nanoparticles is a rapid technology and has advantages over physical and chemical synthesis methods. This research is based on the bacterial formation of silver nanoparticles by bacterial strain Tmas-01. The bacterial strain Tmas-01 was isolated from soil samples and screened for its potential to form Ag/AgCl composite. The formation of Ag/AgCl composite was investigated at the 300–800 nm range using UV–Vis spectrophotometer. Also, the structural and morphological synthesized nanoparticles were characterized using FTIR, SEM–EDS, and XRD. These results showed that Ag/AgCl composite have the SPR absorption peak at 410 nm and a size range of 10–30 nm with a spherical shape. The Ag/AgCl composite exhibited antibacterial and antibiofilm effects against uropathogenic organisms with a range of 5–100%. The results of the genotoxic effects of Ag/AgCl composite by Salmonella typhimurium reverse mutation bioassay (Ames test) indicated which Ag/AgCl composite had no mutation effect. Moreover, Ag/AgCl composite determined an anti-mutagenic effect with a percentage between 97 and 100%. Furthermore, the toxicity of biosynthesized nanoparticles was measured against brine shrimp to evaluate the cytotoxic effect and displayed LC50 (1 µg/ml). The Ag/AgCl composite could effectively photocatalytic degrade up to 64% of Rhodamine B dye. The phylogenetic analysis showed that strain Tmas-01 belonged to Bacillus paralicheniformis sp. with 99.29% similarity.
... In 1959 the great physicist Richard P. Feynman visualized nanotechnology for the first time and he was honored with Nobel Prize in the field for the same. But it was K. Eric Drexler in 1980s did introduce the word Nanotechnology and he meant it for the construction and development of machines in the smallest scale like the size of a molecule which are a few nanometers wide [1]. ...
... Furthermore, the effective surface area in contact with bacterial cells will decrease and result in a decrease in antibacterial activity due to the agglomeration of nanosilver biosynthetic [28]. Nanosilver biosynthetic inhibits bacterial replication by binding and denaturing bacterial DNA [29]. In addition, the nanosilver biosynthetic that accumulates on the surface of bacterial cells will interact with sulfhydryl groups, and release a cationic metal (Ag+), thereby replacing the hydrogen cation (H+) in proteins. ...
Objective: This study aims to formulate nanosliver (AgNPs) biosynthetic hydrogel for topical antibacterial treatment and its stability and antibacterial activity. Methods: The mixture (Silver nitrate solution and Turmeric juice) was stirred at room temperature for 24 h; afterward, it was analyzed using UV-VIS spectrophotometry, particle size analysis, and TEM. The carbopol 940 was selected as a gelling agent with an AgNPs concentration of 5%, 10%, 20%, and 30%. Furthermore, the gel preparation was tested for stability using the cycling test method and antibacterial activity. The antibacterial activity against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. Results: The nanosilver biosynthetic has a yellow-brown color with the maximum wavelength peak at 433 nm, and a particle size of 157.4-166.7 nm. TEM analysis showed that AgNPs have a round shape, while the antibacterial activity of hydrogel preparations was moderately inhibited. Furthermore, the hydrogel was evaluated for pH, viscosity, dispersibility, and antibacterial activity before-after the cycling test. Formula with 30% AgNPs is chosen formula with pH value of 5.87±0.65; viscosity of 4833.3±2.82 c. Ps; and dispersibility of 5.50±0.15 after cycling test. Conclusion: The high concentration of AgNPs will increase the viscosity, pH, and dispersibility. Formula with 30% AgNPs have the highest antibacterial activity. Furthermore, all hydrogel preparations meet the requirements of Indonesian Standard Product (SNI) No. 06-2588-1992 for good gel stability before and after the cycling test.
... The Nanogold-Nanosilver combination can be used as a drug delivery system that will increase the absorption of essential nutrients for the human body [15]. Nanoparticles in gold and silver have the efficiency of increasing the solubility of water-insoluble drugs, accelerating the reaction rate, increasing the half-life of drugs by reducing immunogenicity and so on [23]. In the current condition due to the COVID-19 virus outbreak, one of the efforts to prevent infection and efforts to deal with this virus is by increasing immunity in the body. ...
COVID-19 virus outbreak was first found in Wuhan China. The current COVID-19 is caused by Severe Acute Respiratory Syndrome Coronavirus 2 (Sars-CoV-2). The interaction of the virus with the immune system causes the immunity of people affected by the outbreak to decrease. The combination of nanogold and nanosilver, that is an antimicrobial and antiviral agent, can inhibit the replication of the COVID-19 virus an d act as drug delivery. This research aims to determine the effect of nanogold-nanosilver that can increase immunity in people who are positively affected by the COVID-19 virus. The method used in this research was quantitative descriptive by describing the effect of the nanogold-nanosilver health drink given to increasing human immunity exposed to the COVID-19 virus seen from the number of respondent cures. The respondents consumed 500 mL of health drinks containing nanogold and nanosilver compounds with a concentration of 2 ppm per day. Based on the data obtained, the combination of nanogold and nanosilver could increase the immunity of people affected by COVID-19, marked by physical changes that became healthier, fitter and negative swab test results and accelerate the healing of COVID-19 patients.
... Biological methods include the use of algae to synthesize AgNPs at room temperature [6]; moreover several microorganisms (diatoms, fungi, bacteria) are utilized to grow AgNPs intracellularly or extracellularly such as colonic flora Klebsiella pneumonia, Escherichia coli, Enterobacter cloacae, Bacillus subtilis, Penicillium, Vericillum, Fusarium oxysporum, Pseudomonas stutzeri, Phanerochaete chrysosporium, Penicillium fellutanum, and other [7][8][9][10][11][12][13][14][15][16][17][18][19]. An exceptional work has been done in order to synthesize AgNPs using diverse biological regimes which involve extracts from plants such as Carica papaya, Ocimum, Capsicum annuum, leaves of Azadirachta indica, as well as many other plants [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. The bioreduction ...
This contribution focuses on the green synthesis of silver nanoparticles (AgNPs) with a size < 100 nm for potential medical applications by using silver nitrate solution and Hypericum Perforatum L. (St John’s wort) aqueous extracts. Various synthesis methods were used and compared with regard to their yield and quality of obtained AgNPs. Monodisperse spherical nanoparticles were generated with a size of approximately 20 to 50 nm as elucidated by different techniques (SEM, TEM). XRD measurements showed that metallic silver was formed and the particles possess a face-centered cubic structure (fcc). SEM images and FTIR spectra revealed that the AgNPs are covered by a protective surface layer composed of organic components originating from the plant extract. Ultraviolet-visible spectroscopy, dynamic light scattering, and zeta potential were also measured for biologically synthesized AgNPs. A potential mechanism of reducing silver ions to silver metal and protecting it in the nanoscale form has been proposed based on the obtained results. Moreover, the AgNPs prepared in the present study have been shown to exhibit a high antioxidant activity for 2, 2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, and super oxide anion radical and 2,2-diphenyl-1-picrylhydrazyl. Synthesized AgNPs showed high cytotoxicity by inhibiting cell viability for Hela, Hep G2, and A549 cells.
... More than 48% of strains were sensitive to gentamicin, and it can be reported as the most effective antibiotic (Fig. 5a). From ancient times, silver and its compounds as antimicrobial agents for the treatment of burns, wounds, and other bacterial infections [2]. Increased surface area to volume ratio causes high microbicide activity of silver nanoparticles compared with silver metal [48]. ...
This study investigated the microbial synthesis of Ag/AgCl nanoparticles, their mutagenicity, antimutagenicity and antibacterial effects. For this purpose, bacteria isolates were taken from soil samples of Zarshouran gold mine. One silver resistant bacterial strain was selected for the production of silver nanoparticles. Results of the phylogenetic analysis showed that the strain ZAR1 was 99% similar to Staphylococcus pasteuri. The synthesis of the nanoparticles was confirmed using UV–vis spectroscopy, FTIR, XRD, DLS, and SEM-EDX. The analysis of the nanoparticles synthesized with extracellular extract of bacteria showed that the nanoparticles were spherical with a size of approximately 20–85 nm. Also, the ability of TSB media for the synthesis of silver nanoparticles was evaluated. The formation of Ag/AgCl nanoparticle composites was detected cubic form in the range of 20–50 nm. Antibacterial activity of the nanoparticles was determined against sixty-six pathogenic bacteria. Our results indicated that the nanoparticles had high antimicrobial activity against pathogenic bacteria. Moreover, the nanoparticles stabilized using sodium alginate showed high antimicrobial effects. Ames test revealed that Ag NPs did not display a mutagenic effect. Moreover, the results showed that the nanoparticles were antimutagenic. The percent inhibition of mutagenicity was approximate 97–99%.
... SilvaSorb is also another commercial product used as a wound dressing and as a cavity filler to prevent bacterial infection. Also, it existed as a hand gel used to disinfect skin for personal and clinical hygiene purposes (Mishra & Chauhan, 2015). Gong, Li, and Wang (2018) demonstrated that the green synthesized AgNPs using Euphorbia milii leaf extract exhibited a significant wound healing action in Albino rats. ...
Nanotechnology is a very promising field in several disciplines. Green synthesis techniques are being preferred as more simplistic and eco-friendly approaches for the synthesis of metal/metal oxide nanoparticles than the traditional physical and chemical routes. In recent years, nanoparticles of noble metals such as gold, silver, and palladium have drawn immense attention due to the wide range of their innovative applications in various fields of industry, particularly the biomedical and environmental fields. Thus, it is very important to evaluate their toxicity, to make sure of its biosafety. For instance, silver nanoparticles have attracted significant interest in medical applications, such as diagnosis, treatment, medical device coating, drug delivery, personal health-care products, and as excellent antibacterial agents. Which somehow would approve its biosafety. However, the design and fabrication of nanomaterials with well-controlled physicochemical features and morphological properties to be applied in the human body and environment, remain the focus of many researchers. Nevertheless, the mechanisms for safe utilization, application, and accumulation still need further studies. This chapter aims to discuss the biosafety and medical applications of different green synthesized nanoparticles to approve its recommendation to be applied for pollutant remediation and water treatment. Furthermore, this chapter addresses toxicity issues and the safety rules related to biomedical applications.
... Biological methods include the use of algae to synthesize AgNPs at room temperature [6]; moreover several microorganisms (diatoms, fungi, bacteria) are utilized to grow AgNPs intracellularly or extracellularly such as colonic flora Klebsiella pneumonia, Escherichia coli, Enterobacter cloacae, Bacillus subtilis, Penicillium, Vericillum, Fusarium oxysporum, Pseudomonas stutzeri, Phanerochaete chrysosporium, Penicillium fellutanum, and other [7][8][9][10][11][12][13][14][15][16][17][18][19]. An exceptional work has been done in order to synthesize AgNPs using diverse biological regimes which involve extracts from plants such as Carica papaya, Ocimum, Capsicum annuum, leaves of Azadirachta indica, as well as many other plants [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. The bioreduction ...
Backround and Objectives
A simple and eco- friendly green method was successfully used to synthesis of nano colloidal silver (NCS) using an aqueous extract of Eucalyptus camaldulensis leaves, which acts as a reducing and capping agent.
Method
The goal of this work is to ensure the ability of aqueous extract of Eucalyptus camaldulensis leaves which is widely available in our region cheap and has high antioxidant activities as reducing agent for synthesis of silver nanoparticles. Total phenolic content of extract was evaluated by the well-known colorimetric assay using Folin Ciocalteu reagent. DPPH and ABTS scavenging methods were applied to assessment the antioxidant activities The formation of silver nanoparticles is tested by various techniques like UV-Vis, FTIR-spectroscopy and X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrum (EDX) and Dynamic Light Scattering (DLS). The advantage of our method lies on the fact that Eucalyptus camaldulensis extract acts both as a reducing agent and a stabilizer of silver nanoparticles.
Results and Conclusion
The rapid change of color from yellowish to dark brown within 10 min indicate the high ability of Eucalyptus camaldulensis aqueous extract to reduce Ag+ ions to Ago. FTIR measurements indicated the presence of amine groups which play as capping agent to prevent agglomeration of silver nanoparticles.
... The system working on the board of International Space Station is a good example [9,11]. Moreover, the fabrication of this metal coating on the surface of medical devices or pieces of furniture, and also incorporation of Ag nanoparticles to the building and textile materials, inluences the reduction of the hospital-related infections [12][13][14]. Silver nanoparticles (AgNPs) are also component of many health and cosmetic products due to their antimicrobial activity and deodorizing properties [15,16]. Based on previous results, it is noted that the above-mentioned nanoparticles exhibit antimicrobial activity against 650 strains of pathogenic microorganisms such as bacteria, fungi, viruses, molds, and yeasts [17,18]. ...
... 18 In the present scenario due to the advancement of research in the field of metal nanoparticles, silver nanoparticles attained much more attention than any other metal nanoparticles because of its antimicrobial affinity and therefore are being exploited by many pharmaceutical companies for making antibiotics, used in biomedical applications. 19 Due to antimicrobial affinity of silver nanoparticles, it has so many commercial applications too like manufacturing of washing machines, air conditioners and refrigerators which use linings of silver nanoparticles. [20][21][22][23][24] The medical field also is using products with silver nanoparticles, such as heart valves & other implants, medical face masks, wound dressings and bandages. ...
Tiered risk as sessment approaches for nanomaterial environmental health and safety (nanoEHS) require a detailed understanding of the size and the size distribution of the material being used. There are many metrological tools to choose from, each with its own strengths and weaknesses that influence the results being reported on the exact same batch of material. This review analyzes the physics and metrology in several commonly employed techniques for characterizing nanoparticle (NP) sizes and size distributions and presents how this leads to variations in the reported results. Finally, a case study applying this knowledge to measuring silver (Ag) NP systems is presented, including business-based examples for selecting high-throughput, low-cost measurement approaches for production quality control, and it validates these approaches with goldstandard techniques and statistically significant sampling plans.
The biomedical aspects for the use of nanomaterials obtained by «green nanotechnologies» methods for the diagnosis and treatment of various diseases have been considered. The following advantages of «green nanomaterials» have been noted: product’s low cost, production cycle’s short duration, safety, possibility of the nanoparticle surface modification during manufacturing process. Problems in the «green nanotechnologies» development have been discussed, primarily caused by the lack of measures for standardization and classification of observed therapeutic effects depending on synthesis peculiarities, structure and properties of «green nanomaterials». It has been shown the prospects for the «green nanomaterials» use in the treatment of oncological diseases by methods of photodynamic and photothermal therapy, magnetic resonance imaging, creation of biosensors and antibacterial coatings on the surface of medical materials for the fight against infectious agents, etc. The possibility of «green nanomaterials» directed synthesis for the creation of personal-oriented drugs has been noted. It has been concluded that the medicine of future is, first of all, the personalized multifunctional one, the task of which is prevention, high-precision and timely diagnosis, as well as low-invasive, fast and effective treatment, and an individual safe pharmacological period of rehabilitation, in which drugs and treatment methods based on «green nanomaterials and nanotechnologies» will be widely used.
We studied the effects of course (10 days) intraperitoneal injections of salts of gold and silver and colloid solutions of nanoparticles of these metals on the size (mean value of the cross-sections) of the nuclei of hypothalamic neurocytes localized in the preoptic and arcuate nuclei of immature male albino rats. In animals injected with a solution containing tetrachloroaurate ions, the examined morphometric parameters in both structures significantly exceeded the control values. Injections of gold nanoparticles led to significant decreases in the cross-sections of the neurocyte nuclei; thus, the pattern of the effects of gold depended on its physicochemical form. Injections of both silver salt (AgNO3) and silver nanoparticles led to drops in the mean values of cross-sections of the nuclei of neurocytes. Therefore, shifts of the studied morphofunctional characteristics of the cells belonging to the hypothalamic nuclei resulting from systemic injections of colloid solutions (nanoparticles) of gold and silver are indicative of suppression of functions of the central link of the hypothalamo-hypophyseal-gonadal system after the influence of these factors.
Biosynthesis of nanoparticles by plant extracts is currently under exploitation. Plant extracts are very cost effective and eco-friendly and thus can be an economic and efficient alternative for the large-scale synthesis of nanoparticles. We report on the use of methanolic extract of Eucalyptus hybrida leaf in the extracellular biosynthesis of silver nanoparticles. Bioactive silver nanoparticle synthesis by reacting the methanolic biomass of Eucalyptus hybrida leaf with aqueous solutions of silver nitrate (AgNO 3) at ambient temperature. Formation of silver nanoparticles was confirmed by UV–visible spectroscopy, X-ray diffraction patterns, Scherrer's formula and scanning electron microscopy (SEM) with Energy dispersive X-ray (EDX) patterns. The biomass of plants produces their nanomaterials by a process called biomineralisation. Biological methods are a good competent for the chemical procedures, which are environment friendly and convenient.
Nanosilver particles (NSPs), are among the most attractive nanomaterials, and have been widely used in a range of biomedical applications, including diagnosis, treatment, drug delivery, medical device coating, and for personal health care. With the increasing application of NSPs in medical contexts, it is becoming necessary for a better understanding of the mechanisms of NSPs’ biological interactions and their potential toxicity. In this review, we first introduce the synthesis routes of NSPs, including physical, chemical, and biological or green synthesis. Then the unique physiochemical properties of NSPs, such as antibacterial, antifungal, antiviral, and anti-inflammatory activity, are discussed in detail. Further, some recent applications of NSPs in prevention, diagnosis, and treatment in medical fields are described. Finally, potential toxicology considerations of NSPs, both in vitro and in vivo, are also addressed.
The metallic nanoparticles have great attention of Chemists, Physists, Biologists and Engineers who wish to use them for development of new generation nanodevices. In this present study silver nanoparticles were synthesized from aqueous silver nitrate (1mM) through a simple and eco-friendly route using leaf broth of Ocimum sanctum as reductant and stabilizer. The aqueous silver ions when exposed to leaf broth were reduced and resulted in the green synthesis of silver nanoparticles ranges from 3-20 nm. The bioreduced silver nanoparticles were characterized by UV-Vis spectrophotometer, X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier transform infra-red (FTIR) spectroscopy. The observed peaks in XRD pattern corresponding to (111), (200) and (311) planes. The FTIR measurement was carried out to identify the possible biomolecules responsible for efficient stabilization of silver nanoparticles
Background
Silver nanoparticles (AgNP), the most popular nano-compounds, possess unique properties. Albizia adianthifolia (AA) is a plant of the Fabaceae family that is rich in saponins. The biological properties of a novel AgNP, synthesized from an aqueous leaf extract of AA (AAAgNP), were investigated on A549 lung cells. Cell viability was determined by the MTT assay. Cellular oxidative status (lipid peroxidation and glutathione (GSH) levels), ATP concentration, caspase-3/-7, -8 and −9 activities were determined. Apoptosis, mitochondrial (mt) membrane depolarization (flow cytometry) and DNA fragmentation (comet assay) were assessed. The expression of CD95 receptors, p53, bax, PARP-1 and smac/DIABLO was evaluated by flow cytometry and/or western blotting.
Results
Silver nanoparticles of AA caused a dose-dependent decrease in cell viability with a significant increase in lipid peroxidation (5-fold vs. control; p = 0.0098) and decreased intracellular GSH (p = 0.1184). A significant 2.5-fold decrease in cellular ATP was observed upon AAAgNP exposure (p = 0.0040) with a highly significant elevation in mt depolarization (3.3-fold vs. control; p < 0.0001). Apoptosis was also significantly higher (1.5-fold) in AAAgNP treated cells (p < 0.0001) with a significant decline in expression of CD95 receptors (p = 0.0416). Silver nanoparticles of AA caused a significant 2.5-fold reduction in caspase-8 activity (p = 0.0024) with contrasting increases in caspase-3/-7 (1.7-fold vs. control; p = 0.0180) and −9 activity (1.4-fold vs. control; p = 0.0117). Western blots showed increased expression of smac/DIABLO (4.1-fold) in treated cells (p = 0.0033). Furthermore, AAAgNP significantly increased the expression of p53, bax and PARP-1 (1.2-fold; p = 0.0498, 1.6-fold; p = 0.0083 and 1.1-fold; p = 0.0359 respectively).
Conclusion
Data suggests that AAAgNP induces cell death in the A549 lung cells via the mt mediated intrinsic apoptotic program. Further investigation is required to potentiate the use of this novel compound in cancer therapy trials.
A simple and economic method of synthesis of silver colloid nanoparticles with controlled size is presented. By reduction of [Ag(NH3)2]+ complex in sodium dodecylsulfate (SDS) micellar solution with three various reducing agents (hydrazine, formalin and ascorbic acid) the nanoparticles were produced with size below 20 nm. The average size, size distribution, morphology, and structure of particles were determined by dynamic light scattering (DLS), scanning electron microscopy (SEM), and UV/Visible absorption spectrophotometry. The influence of the reducing agent on the size of silver particles, fraction of metallic silver and their antimicrobial properties is discussed. In particular, the reduction of silver complex by hydrazine resulted in silver nanoparticles with size below 20nm. They showed high activity against Gram-positive and Gram-negative bacteria (lab isolated strains), and clinical isolated strains including highly multiresistant strains such as Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa.
There is an increasing commercial demand for nanoparticles due to their wide applicability in various areas such as electronics, catalysis, chemistry, energy, and medicine. Metallic nanoparticles are traditionally synthesized by wet chemical techniques, where the chemicals used are quite often toxic and flammable. In this work, we describe a cost effective and environment friendly technique for green synthesis of silver nanoparticles from 5mM AgNO 3 solution through the extract of Argemone maxicana leaf extract as reducing agent as well as capping agent. Nanoparticles were characterized using UV–Vis absorption spectroscopy, FTIR, XRD and SEM. X-ray diffraction and SEM analysis showed the average particle size of 30 nm as well as revealed their structure. Further these biologically synthesized nanoparticles were found to be highly toxic against different bacterial spp. The most important outcome of this work will be the development of value-added products from Argemone maxicana (a potential weed of India) for biomedical and nanotechnology based industries. This is for the first time that Argemone maxicana weed leaf extract was used for the synthesis of nanoparticles.
Scientific publications and patents on nanomaterials (NM) used in plant protection or fertilizer products have exponentially increased since the millennium shift. While the United States and Germany have published the highest number of patents, Asian countries released most scientific articles. About 40% of all contributions deal with carbon-based NM, followed by titanium dioxide, silver, silica, and alumina. Nanomaterials come in many diverse forms (surprisingly often ≫100 nm), from solid doped particles to (often nonpersistent) polymer and oil-water based structures. Nanomaterials serve equally as additives (mostly for controlled release) and active constituents. Product efficiencies possibly increased by NM should be balanced against enhanced environmental NM input fluxes. The dynamic development in research and its considerable public perception are in contrast with the currently still very small number of NM-containing products on the market. Nanorisk assessment and legislation are largely in their infancies.
A silver resistant Bacillus sp. was isolated through exposure of an aqueous AgNO3 solution to the atmosphere. Silver nanoparticles were synthesized using these airborne bacteria (Bacillus sp.). Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analyses confirmed that silver nanoparticles
of 5–15nm in size were deposited in the periplasmic space of the bacterial cells; a preferable cell surface location for
the easy recovery of biogenic nanoparticles.
We have successfully produced silver nanoparticles by irradiating an Ag target with a 532-nm laser beam in pure water. By working with high laser power and small spot sizes, we were able to synthesize very small spherical particles with a typical size of 2–5nm. The influence of the beam spot size, the laser power, and the ablation time were studied, and the possible mechanisms of particle formation are discussed.
Experimental composite adhesives (ECAs) containing silica nanofillers and silver nanoparticles were compared with two conventional adhesives (composite and resin-modified glass ionomer [RMGI]) to analyze surface characteristics, physical properties and antibacterial activities against cariogenic streptococci.
Surface roughness and surface free energy (SFE) characteristics were measured using confocal laser scanning microscopy and the sessile drop method. Shear bond strength and bond failure interface were analyzed to compare the physical properties. Antimicrobial activities were analyzed by a bacterial adhesion assay, a disk diffusion test, and an optical density measurement of bacterial suspension containing each adhesive.
ECAs had rougher surfaces than conventional adhesives due to the addition of silver nanoparticles. ECAs had more similar SFE characteristics to composite than to RMGI. Bacterial adhesion to ECAs was less than to conventional adhesives, which was not influenced by saliva coating. Bacterial suspension containing ECAs showed slower bacterial growth than those containing conventional adhesives. There was no significant difference in shear bond strength and bond failure interface between ECAs and conventional adhesives.
This study suggests that ECAs can help prevent enamel demineralization around their surfaces without compromising physical properties.
Although nanoparticles have tremendous potential for a host of applications, their adverse effects on living cells have raised serious concerns recently for their use in the healthcare and consumer sectors. As regards the central nervous system (CNS), research data on nanoparticle interaction with neurons has provided evidence of both negative and positive effects. Maximal application dosage of nanoparticles in materials to provide applications such as antibacterial and antiviral functions is approximately 0.1-1.0 wt%. This concentration can be converted into a liquid phase release rate (leaching rate) depending upon the host or base materials used. For example, nanoparticulate silver (Ag) or copper oxide (CuO)-filled epoxy resin demonstrates much reduced release of the metal ions (Ag(+) or Cu(2+)) into their surrounding environment unless they are mechanically removed or aggravated. Subsequent to leaching effects and entry into living systems, nanoparticles can also cross through many other barriers, such as skin and the blood-brain barrier (BBB), and may also reach bodily organs. In such cases, their concentration or dosage in body fluids is considered to be well below the maximum drug toxicity test limit (10(-5) g ml(-1)) as determined in artificial cerebrospinal solution. As this is a rapidly evolving area and the use of such materials will continue to mature, so will their exposure to members of society. Hence, neurologists have equal interests in nanoparticle effects (positive functionality and negative toxicity) on human neuronal cells within the CNS, where the current research in this field will be highlighted and reviewed.
Silver nanoparticles have proven to exert antiviral activity against HIV-1 at non-cytotoxic concentrations, but the mechanism underlying their HIV-inhibitory activity has not been not fully elucidated. In this study, silver nanoparticles are evaluated to elucidate their mode of antiviral action against HIV-1 using a panel of different in vitro assays.
Our data suggest that silver nanoparticles exert anti-HIV activity at an early stage of viral replication, most likely as a virucidal agent or as an inhibitor of viral entry. Silver nanoparticles bind to gp120 in a manner that prevents CD4-dependent virion binding, fusion, and infectivity, acting as an effective virucidal agent against cell-free virus (laboratory strains, clinical isolates, T and M tropic strains, and resistant strains) and cell-associated virus. Besides, silver nanoparticles inhibit post-entry stages of the HIV-1 life cycle.
These properties make them a broad-spectrum agent not prone to inducing resistance that could be used preventively against a wide variety of circulating HIV-1 strains.
Silver nanoparticles in the size range of 2-5 nm were synthesized extracellularly by a silver-tolerant yeast strain MKY3, when challenged with 1 mM soluble silver in the log phase of growth. The nanoparticles were separated from dilute suspension by devising a new method based on differential thawing of the sample. Optical absorption, transmission electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy investigations confirmed that metallic (elemental) silver nanoparticles were formed. Extracellular synthesis of nanoparticles could be highly advantageous from the point of view of synthesis in large quantities and easy downstream processing.
Nanotechnology will affect our lives tremendously over the next decade in very different fields, including medicine and pharmacy. Transfer of materials into the nanodimension changes their physical properties which were used in pharmaceutics to develop a new innovative formulation principle for poorly soluble drugs: the drug nanocrystals. The drug nanocrystals do not belong to the future; the first products are already on the market. The industrially relevant production technologies, pearl milling and high pressure homogenization, are reviewed. The physics behind the drug nanocrystals and changes of their physical properties are discussed. The marketed products are presented and the special physical effects of nanocrystals explained which are utilized in each market product. Examples of products in the development pipelines (clinical phases) are presented and the benefits for in vivo administration of drug nanocrystals are summarized in an overview.
Silver compounds are used as antimicrobial agents in medicine and bacteria that develop resistance to silver cations (Ag(+)) pose problems similar to those of antibiotic-resistant bacteria. The first set of Ag(+) resistance genes (sil) was from plasmid pMG101, now assigned to the IncHI incompatibility group. Questions of whether sil genes are unique to pMG101 or are more widely found, and whether they are associated with a specific incompatibility group or occur in many plasmid groups and on bacterial chromosomes were addressed. sil genes were identified in five IncH plasmids, but not in plasmids of the IncP incompatibility group. Three sil genes (silP, silR and silE) from these plasmids were PCR-amplified, cloned, sequenced and compared to those of pMG101. Differences of 0-50 nt per kb of sequence were found. Predicted gene products were 0-6% different in amino acid sequence, but the differences did not alter residues thought to be involved in protein function (see supplementary data at http://mic.sgmjournals.org or http://www.uic.edu/depts/mcmi/individual/gupta/index.htm). For representative IncH plasmid R476b and pMG101 the effects of Ag(+) exposure on resistance levels were measured by growth. The inducibility of silC, silR and silE gene expression after Ag(+) exposure was studied by reverse transcriptase (RT)-PCR. Silver resistance increased after Ag(+) exposure for strains carrying plasmid R476b. silC and silE expression from R476b was inducible after Ag(+) exposure and was constitutive and high from pMG101. The mRNA levels for the regulatory gene silR was constitutive for both pMG101 and R476b. Close homologues for silABC(ORF96)RS from pMG101 are clustered on the chromosomes of Escherichia coli strains K-12 and O157:H7, without contiguous silP and silE homologues. Insertion deletions of the E. coli K-12 chromosomal homologues for silA and silP gave Ag(+) hypersensitivity for growth. The silA homologue knockout was complemented back to wild-type resistance by the same gene cloned on a plasmid. Homologues of sil genes have also been identified on other enterobacterial genomes.
To study the epidemiology of Pseudomonas aeruginosa colonization in a 32-bed burn wound center (BWC), 321 clinical and 45 environmental P. aeruginosa isolates were collected by prospective surveillance culture over a 1-year period and analyzed by serotyping, drug susceptibility testing, and amplified fragment length polymorphism (AFLP) analysis. Among 441 patients treated at the center, 70 (16%) were colonized with P. aeruginosa, including 12 (17%) patients who were colonized on admission and 58 (83%) patients who acquired the organism during their stay. Of the 48 distinct AFLP genotypes found, 21 were found exclusively in the environment, 15 were isolated from individual patients only, and 12 were responsible for the colonization of 57 patients, of which 2 were also isolated from the environment, but secondary to patient carriage. Polyclonal P. aeruginosa colonization with strains of two to four genotypes, often with different antibiotic susceptibility patterns, was observed in 19 patients (27%). Two predominant genotypes were responsible for recurrent outbreaks and the colonization of 42 patients (60% of all colonized patients). The strain with one of those genotypes appeared to be endemic to the BWC and developed multidrug resistance (MDR) at the end of the study period, whereas the strain with the other genotype was antibiotic susceptible but resistant to silver sulfadiazine (SSD(r)). The MDR strain was found at a higher frequency in sputum samples than the SSD(r) strain, which showed a higher prevalence in burn wound samples, suggesting that anatomic habitat selection was associated with adaptive resistance to antimicrobial drugs. Repeated and thorough surveys of the hospital environment failed to detect a primary reservoir for any of those genotypes. Cross-acquisition, resulting from insufficient compliance with infection control measures, was the major route of colonization in our BWC. In addition to the AFLP pattern and serotype, analysis of the nucleotide sequences of three (lipo)protein genes (oprI, oprL, and oprD) and the pyoverdine type revealed that all predominant strains except the SSD(r) strain belonged to recently identified clonal complexes. These successful clones are widespread in nature and therefore predominate in the patient population, in whom variants accumulate drug resistance mechanisms that allow their transmission and persistence in the BWC.
The interaction of nanoparticles with biomolecules and microorganisms is an expanding field of research. Within this field, an area that has been largely unexplored is the interaction of metal nanoparticles with viruses. In this work, we demonstrate that silver nanoparticles undergo a size-dependent interaction with HIV-1, with nanoparticles exclusively in the range of 1-10 nm attached to the virus. The regular spatial arrangement of the attached nanoparticles, the center-to-center distance between nanoparticles, and the fact that the exposed sulfur-bearing residues of the glycoprotein knobs would be attractive sites for nanoparticle interaction suggest that silver nanoparticles interact with the HIV-1 virus via preferential binding to the gp120 glycoprotein knobs. Due to this interaction, silver nanoparticles inhibit the virus from binding to host cells, as demonstrated in vitro.
The aim of this paper is to present the harmonisation of the global medical textile market and the categories of medical textiles based on their applications. The paper also contains an analysis of some trends in the foreign trade of medical textiles on the world economy.
Nanotechnology is multidisciplinary field that involves the design and engineering of objects <500 nanometers (nm) in size. These have been applied to improve drug delivery and to overcome some of the problems of drug delivery in cancer. These can be classified into many categories that include use of various nanoparticles, nanoencapsulation, targeted delivery to tumors of various organs, and combination with other methods of treatment of cancer such as radiotherapy. Nanoparticles are also used for gene therapy for cancer. This review explores recent work directed towards more targeted treatment of cancer, whether through more specific anti-cancer agents or through methods of delivery. A part of these, Sonophoresis is also a tool to enhance bioavailability and solubility of drug and also a useful tool to enhance permeability of anticancer agents.
The revolutionary Feynman vision of a powerful and general nanotechnology, based on nanomachines that build with atom-by-atom control, promises great opportunities and, if abused, great dangers. This vision made nanotechnology a buzzword and launched the global nanotechnology race. Along the way, however, the meaning of the word has shifted. A vastly broadened definition of nanotechnology (including any technology with nanoscale features) enabled specialists from diverse fields to infuse unrelated research with the Feynman mystique. The resulting nanoscaletechnology funding coalition has obscured the Feynman vision by misunderstanding its basis, distrusting its promise, and fearing that public concern regarding its dangers might interfere with research funding. In response, leaders of a funding coalition have attempted to narrow nanotechnology to exclude one area of nanoscale technology—the Feynman vision itself. Their misdirected arguments against the Feynman vision have needlessly confused public discussion of the objectives and consequences of nanotechnology research.
Using four kinds of antibiotics, an investigation was made to determine whether or not H2O2 generated from a ZnO powder slurry was related to its antibacterial activity. Changes in the sensitivity of Escherichia coli to the antibiotics suggested that H2O2 was one of the primary factors concerned in the antibacterial activity of the ZnO powder slurry.
The reliability and performance of a domestic refrigerator with nanoparticles in the working fluid was investigated experimentally. Mineral oil with TiO2 nanoparticles mixtures were used as the lubricant instead of Polyol-ester (POE) oil in the 1,1,1,2-tetrafluoroethane (HFC134a) refrigerator. The compatibility of nonmetallic materials in the system with the HFC134a and mineral oil–nanoparticles mixtures was studied before the refrigerator performance tests. The refrigerator performance with the nanoparticles was then investigated using energy consumption tests and freeze capacity tests. The results indicate that HFC134a and mineral oil with TiO2 nanoparticles works normally and safely in the refrigerator. The refrigerator performance was better than the HFC134a and POE oil system, with 26.1% less energy consumption used with 0.1% mass fraction TiO2 nanoparticles compared to the HFC134a and POE oil system. The same tests with Al2O3 nanoparticles showed that the different nanoparticles properties have little effect on the refrigerator performance. Thus, nanoparticles can be used in domestic refrigerators to considerably reduce energy consumption.
Silver nanoparticles (NPs) were rapidly synthesized by treating silver ions with a Capsicum annuum L. extract. The reaction process was simple and convenient to handle, and was monitored using ultraviolet-visible spectroscopy (UV-vis). The effect of Capsicum annuum L. proteins on the formation of silver NPs was investigated using X-ray photoemission spectroscopy (XPS), electrochemical measurements, Fourier-transform infrared spectroscopy (FTIR) and differential spectrum techniques. The morphology and crystalline phase of the NPs were determined from transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD) spectra. The results indicated that the proteins, which have amine groups, played a reducing and controlling role during the formation of silver NPs in the solutions, and that the secondary structure of the proteins changed after reaction with silver ions. The crystalline phase of the NPs changed from polycrystalline to single crystalline and increased in size with increasing reaction time. A recognition–reduction–limited nucleation and growth model was suggested to explain the possible formation mechanism of silver NPs in Capsicum annuum L. extract.
Scientific community believe that nanotechnology offers new ways to address residual scientific concerns for Mycobacterium tuberculosis (TB). Nanoparticle-based systems have significant prospective for diagnosis, treatment and prevention of tuberculosis (TB). Nanoparticles based tuberculosis diagnostic kits are under trial and have fascinating in sense that it is not required skilled hand and also have low cost. Another significant advancement of this technology is that the using of nano particles as drug carriers are has high stability and carrier capacity. The possibility of drug administration by oral and inhalation route make it more advantageous. The controlled drug release from the matrix, such properties of nanoparticles enable improvement of drug bioavailability and reduction of the dosing frequency, and may resolve the problem of non adherence to prescribed therapy. The development of aerosol vaccine is undergoing which could provide a great potential in prevention of tuberculosis infection. Keeping in mind the role of nanoparticles in these three aspects like diagnosis, treatment and prevention of tuberculosis, this article is the attempts to compile these aspects in hope for better advancements.
Extracellular biosynthesis of silver nanoparticles by Aspergillus niger isolated from soil is being reported in the present paper. The production of silver nanoparticles was evidenced by UV-vis spectrum, showing the absorbance at 420nm (Perkin Elmer Lambda-25). The nanoparticles characterized by Transmission Electron Microscopy exhibited spherical silver nanoparticles with diameter of around 20nm. Elemental Spectroscopy imaging showed the presence of fungal protein around the silver nanoparticles thereby increasing their stability in the suspension. The silver nanoparticles (10 μg/ml) showed remarkable antibacterial activity against gram-positive (Staphylococcus. aureus) and gram-negative (Escherichia coli) bacteria. The reduction of the silver ions might have occurred by a nitrate-dependent reductase enzyme and a shuttle quinone extracellular process. Reduction of silver ions was an extracellular and rapid process; this knowledge may lead to the development of an easy process for biosynthesis of the silver nanoparticles. Potential of fungal-mediated biosynthesis of silver nanoparticles is important for development of effective antibacterial agents showing resistance to drugs available in the market.
Silver is extremely toxic to a wide range of bacteria1–5, and has even been used in solution to control bacterial growth2. In an investigation of the oxidation of several sulphide minerals containing traces of silver by a mixed culture of Thiobadllus ferroxidans and Thiobacillus thiooxidans, it was noted that the bacteria accumulated silver. I report here that careful collection of most of the cells from such experiments yields a silver concentrate, while the silver attached to the cells remaining in contact with leach residues is readily recovered by a conventional cyanidation technique. These results suggest that the bacterial leaching of valuable and non-valuable sulphide minerals in order to release atomically bound silver, and possibly gold, may be used as part of a recovery process for these elements.
The fate of nanoparticles in organisms is of significant interest. In the current work, we used a test system with terrestrial isopods (Porcellio scaber) fed with food spiked with Cu NPs or soluble Cu salt for 14 days. Two different doses were used for spiking to yield final concentrations of 2000 and 5000 μg Cu/g dry food. After the exposure period, part of the exposed group of animals was transferred to clean food to depurate. Cu content was analyzed in the digestive glands, gut, and the 'rest' of the body. Similar patterns of (i) assimilated and depurated amounts of Cu, (ii) Cu body distribution, and (iii) effect on isopods feeding behavior were observed regardless of whether the animals were fed with Cu NPs or soluble Cu salt spiked food. Thus, Cu ions and not Cu NPs were assimilated by the digestive gland cells. Solubilization of the Cu NPs applied to the leaves was also analyzed with chemical methods and recombinant Cu-sensing bacteria. The comparison of the in vitro data on solubilization of Cu NPs and in vivo data on Cu accumulation in the animal tissues showed that about 99% of accumulated copper ions was dissolved from ingested Cu NPs in the digestive system of isopods.
The interaction of metal atoms, clusters and nanoparticles with different organic and inorganic substances were studied at low temperature (10–40K). Combination of matrix isolation technique and preparative cryochemistry was applied for the investigation of activity and selectivity of metal particles of different size. Encapsulation of metal nanoparticles in polymers was studied. The metal–polymer films thus obtained exhibited satisfactory sensitivity to ammonia.
Silver nanoparticles were successfully synthesized from AgNO3 through a simple green route using the latex of Jatropha curcas as reducing as well as capping agent. Nanoparticles were characterized with the help of HRTEM, X-ray diffraction and UV–vis absorption spectroscopy. X-ray diffraction analysis showed that the nanoparticles were of face centered cubic structure. A comparison of radius of nanoparticles obtained from HRTEM image with the optimized cavity radius of the cyclic peptides present within the latex revealed that the particles having radius 10–20 nm are mostly stabilized by the cyclic peptides.
The development of reliable, eco-friendly processes for the synthesis of nanomaterials is an important aspect of nanotechnology today. One approach that shows immense potential is based on the biosynthesis of nanoparticles using biological micro-organisms such as bacteria. In this laboratory, we have concentrated on the use of fungi in the intracellular production of metal nanoparticles. As part of our investigation, we have observed that aqueous silver ions when exposed to the fungus Fusarium oxysporum are reduced in solution, thereby leading to the formation of an extremely stable silver hydrosol. The silver nanoparticles are in the range of 5–15 nm in dimensions and are stabilized in solution by proteins secreted by the fungus. It is believed that the reduction of the metal ions occurs by an enzymatic process, thus creating the possibility of developing a rational, fungal-based method for the synthesis of nanomaterials over a range of chemical compositions, which is currently not possible by other microbe-based methods.
An overview of methods for preparing nanoparticles in the vapor phase is given, and recent advances are reviewed. Developments in instrumentation for monitoring vapor-phase synthesis of nanoparticles and in modeling these processes are also included. The most important developments relate to improved control and understanding of nanoparticle aggregation and coalescence during synthesis, and to methods for producing multi-component nanoparticles.
Biological synthesis of gold and silver nanoparticles of various shapes using the leaf extract of Hibiscus rosa sinensis is reported. This is a simple, cost-effective, stable for long time and reproducible aqueous room temperature synthesis method to obtain a self-assembly of Au and Ag nanoparticles. The size and shape of Au nanoparticles are modulated by varying the ratio of metal salt and extract in the reaction medium. Variation of pH of the reaction medium gives silver nanoparticles of different shapes. The nanoparticles obtained are characterized by UV–vis, transmission electron microscopy (TEM), X-ray diffraction (XRD) and FTIR spectroscopy. Crystalline nature of the nanoparticles in the fcc structure are confirmed by the peaks in the XRD pattern corresponding to (1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes, bright circular spots in the selected area electron diffraction (SAED) and clear lattice fringes in the high-resolution TEM image. From FTIR spectra it is found that the Au nanoparticles are bound to amine groups and the Ag nanoparticles to carboxylate ion groups.
Here, we present a review of the antibacterial effects of silver nanomaterials, including proposed antibacterial mechanisms and possible toxicity to higher organisms. For purpose of this review, silver nanomaterials include silver nanoparticles, stabilized silver salts, silver–dendrimer, polymer and metal oxide composites, and silver-impregnated zeolite and activated carbon materials. While there is some evidence that silver nanoparticles can directly damage bacteria cell membranes, silver nanomaterials appear to exert bacteriocidal activity predominantly through release of silver ions followed (individually or in combination) by increased membrane permeability, loss of the proton motive force, inducing de-energization of the cells and efflux of phosphate, leakage of cellular content, and disruption DNA replication. Eukaryotic cells could be similarly impacted by most of these mechanisms and, indeed, a small but growing body of literature supports this concern. Most antimicrobial studies are performed in simple aquatic media or cell culture media without proper characterization of silver nanomaterial stability (aggregation, dissolution, and re-precipitation). Silver nanoparticle stability is governed by particle size, shape, and capping agents as well as solution pH, ionic strength, specific ions and ligands, and organic macromolecules—all of which influence silver nanoparticle stability and bioavailability. Although none of the studies reviewed definitively proved any immediate impacts to human health or the environment by a silver nanomaterial containing product, the entirety of the science reviewed suggests some caution and further research are warranted given the already widespread and rapidly growing use of silver nanomaterials.
Nanosilver (NS), comprising silver nanoparticles, is attracting interest for a range of biomedical applications owing to its potent antibacterial activity. It has recently been demonstrated that NS has useful anti-inflammatory effects and improves wound healing, which could be exploited in developing better dressings for wounds and burns. The key to its broad-acting and potent antibacterial activity is the multifaceted mechanism by which NS acts on microbes. This is utilized in antibacterial coatings on medical devices to reduce nosocomial infection rates. Many new synthesis methods have emerged and are being evaluated for NS production for medical applications. NS toxicity is also critically discussed to reflect on potential concerns before widespread application in the medical field.
The antifungal activity of the silver nanoparticles (NPs) prepared by the modified Tollens process was evaluated for pathogenic Candida spp. by means of the determination of the minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), and the time-dependency of yeasts growth inhibition. Simultaneously the cytotoxicity of the silver NPs to human fibroblasts was determined. The silver NPs exhibited inhibitory effect against the tested yeasts at the concentration as low as 0.21 mg/L of Ag. The inhibitory effect of silver NPs was enhanced through their stabilization and the lowest MIC equal to 0.05 mg/L was determined for silver NPs stabilized by sodium dodecyl sulfate against Candida albicans II. The obtained MICs of the silver NPs and especially of the stabilized silver NPs were comparable and in some cases even better than MICs of the conventional antifungal agents determined by E-test. The silver NPs effectively inhibited the growth of the tested yeasts at the concentrations below their cytotoxic limit against the tested human fibroblasts determined at a concentration equal to 30 mg/L of Ag. In contrast, ionic silver inhibited the growth of the tested yeasts at the concentrations comparable to the cytotoxic level (approx. 1mg/L) of ionic silver against the tested human fibroblasts.
The exploitation of various plant materials for the biosynthesis of nanoparticles is considered a green technology as it does not involve any harmful chemicals. The present study reports the synthesis of silver (Ag) nanoparticles from silver precursor using the bark extract and powder of novel Cinnamon zeylanicum. Water-soluble organics present in the plant materials were mainly responsible for the reduction of silver ions to nano-sized Ag particles. TEM and XRD results confirmed the presence of nano-crystalline Ag particles. The pH played a major role in size control of the particles. Bark extract produced more Ag nanoparticles than the powder did, which was attributed to the large availability of the reducing agents in the extract. Zeta potential studies showed that the surface charge of the formed nanoparticles was highly negative. The EC(50) value of the synthesized nanoparticles against Escherichia coli BL-21 strain was 11+/-1.72 mg/L. Thus C. zeylanicum bark extract and powder are a good bio-resource/biomaterial for the synthesis of Ag nanoparticles with antimicrobial activity.
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.
One mechanism of silver resistance in microorganisms is accumulation of the metal ions in the cell. Here, we report on the phenomenon of biosynthesis of silver-based single crystals with well-defined compositions and shapes, such as equilateral triangles and hexagons, in Pseudomonas stutzeri AG259. The crystals were up to 200 nm in size and were often located at the cell poles. Transmission electron microscopy, quantitative energy-dispersive x-ray analysis, and electron diffraction established that the crystals comprise at least three different types, found both in whole cells and thin sections. These Ag-containing crystals are embedded in the organic matrix of the bacteria. Their possible potential as organic-metal composites in thin film and surface coating technology is discussed.
This Account reviews our laboratory's research in biomaterials. In one area, drug delivery, we discuss the development of materials that are capable of releasing macromolecules such as proteins and peptides, intelligent delivery systems based on magnetism or microchip technology, new degradable materials such as polyanhydrides, and noninvasive approaches for delivering molecules through the skin and lungs. A second area, tissue engineering, is also discussed. New polymer systems for creating cartilage, blood vessels, nerves, and other tissues are examined.
A novel nanoparticle-based drug carrier for photodynamic therapy is reported which can provide stable aqueous dispersion of hydrophobic photosensitizers, yet preserve the key step of photogeneration of singlet oxygen, necessary for photodynamic action. A multidisciplinary approach is utilized which involves (i) nanochemistry in micellar cavity to produce these carriers, (ii) spectroscopy to confirm singlet oxygen production, and (iii) in vitro studies using tumor cells to investigate drug-carrier uptake and destruction of cancer cells by photodynamic action. Ultrafine organically modified silica-based nanoparticles (diameter approximately 30 nm), entrapping water-insoluble photosensitizing anticancer drug 2-devinyl-2-(1-hexyloxyethyl) pyropheophorbide, have been synthesized in the nonpolar core of micelles by hydrolysis of triethoxyvinylsilane. The resulting drug-doped nanoparticles are spherical, highly monodispersed, and stable in aqueous system. The entrapped drug is more fluorescent in aqueous medium than the free drug, permitting use of fluorescence bioimaging studies. Irradiation of the photosensitizing drug entrapped in nanoparticles with light of suitable wavelength results in efficient generation of singlet oxygen, which is made possible by the inherent porosity of the nanoparticles. In vitro studies have demonstrated the active uptake of drug-doped nanoparticles into the cytosol of tumor cells. Significant damage to such impregnated tumor cells was observed upon irradiation with light of wavelength 650 nm. Thus, the potential of using ceramic-based nanoparticles as drug carriers for photodynamic therapy has been demonstrated.
The worldwide emergence of nanoscale science and engineering was marked by the announcement of the National Nanotechnology Initiative (NNI) in January 2000. Recent research on biosystems at the nanoscale has created one of the most dynamic science and technology domains at the confluence of physical sciences, molecular engineering, biology, biotechnology and medicine. This domain includes better understanding of living and thinking systems, revolutionary biotechnology processes, the synthesis of new drugs and their targeted delivery, regenerative medicine, neuromorphic engineering and developing a sustainable environment. Nanobiosystems research is a priority in many countries and its relevance within nanotechnology is expected to increase in the future.
Multidrug resistance (MDR) has been reported in both prokaryotes and eukaryotes, underscoring the challenge of design and screening of more efficacious new drugs. For instance, the efflux pump of Pseudomonas aeruginosa (gram-negative bacteria) can extrude a variety of structurally and functionally diverse substrates, which leads to MDR. In this study, we present a new platform that studies modes of action of antibiotics in living bacterial cells (P. aeruginosa), in real-time, at nanometer scale and single-cell resolution using nanoparticle optics and single living cell imaging. The color index of silver (Ag) nanoparticles (violet, blue, green, and red) is used as the sized index (30 +/- 10, 50 +/- 10, 70 +/- 10, and 90 +/- 10 nm) for real-time measurement of sized transformation of the cell wall and membrane permeability at the nanometer scale. We have demonstrated that the number of Ag nanoparticles accumulated in cells increases as the aztreonam (AZT) concentration increases and as incubation time increases, showing that AZT induces the sized transformation of membrane permeability and the disruption of the cell wall. The results demonstrate that nanoparticle optics assay can be used as a new powerful tool for real-time characterization of modes of action of antimicrobial agents in living cells at the nanometer scale. Furthermore, studies of mutants of WT bacteria (nalB-1 and DeltaABM), suggest that an efflux pump (MexA-MexB-OprM) effectively extrudes substrates (nanoparticles) out of the cells, indicating that the MDR mechanism involves the induction of changes in membrane permeability and the intrinsic pump machinery.
The antimicrobial activity of silver nanoparticles against E. coli was investigated as a model for Gram-negative bacteria. Bacteriological tests were performed in Luria-Bertani (LB) medium on solid agar plates and in liquid systems supplemented with different concentrations of nanosized silver particles. These particles were shown to be an effective bactericide. Scanning and transmission electron microscopy (SEM and TEM) were used to study the biocidal action of this nanoscale material. The results confirmed that the treated E. coli cells were damaged, showing formation of "pits" in the cell wall of the bacteria, while the silver nanoparticles were found to accumulate in the bacterial membrane. A membrane with such a morphology exhibits a significant increase in permeability, resulting in death of the cell. These nontoxic nanomaterials, which can be prepared in a simple and cost-effective manner, may be suitable for the formulation of new types of bactericidal materials.
MK-0869 (aprepitant), a potent substance P antagonist, is the active ingredient of EMEND which has recently been approved by the FDA for the prevention of chemotherapy-induced nausea and vomiting. Early clinical tablet formulations of MK-0869 showed significant food effects on absorption, suggesting that formulation could have a significant role in improving bioavailability. A Beagle dog model was developed in an effort to guide novel formulation development. Using the suspension of the micronized bulk drug used for the tablet formulations, the food effect on absorption was confirmed in the dog at a similar magnitude to that observed in humans. Further dog studies demonstrated a clear correlation between particle size and in vivo exposures, with the nanoparticle (NanoCrystal) colloidal dispersion formulation providing the highest exposure, suggesting dissolution-limited absorption. The NanoCrystal dispersion also eliminated the food effect on oral absorption in the dog at a dose of 2mg/kg. Regional absorption studies using triport dogs indicated that the absorption of MK-0869 was limited to the upper gastrointestinal tract. These results provided strong evidence that the large increase in surface areas of the drug nanoparticles could overcome the narrow absorption window and lead to rapid in vivo dissolution, fast absorption, and increased bioavailability. In addition, the dog model was used for optimizing formulation processes in which the nanoparticles were incorporated into solid dosage forms, and for selecting excipients to effectively re-disperse the nanoparticles from the dosage units. The human pharmacokinetic data using the nanoparticle formulation showed excellent correlations with those generated in the dog.
Nanotechnology, which involves investigating and manipulating matter at the atomic and molecular levels, may radically transform industry and society. Because nanotechnology could introduce whole new classes of materials and products, it could present an array of novel challenges to regulatory agencies. In this note, John Miller explores the regulatory challenges facing the Food and Drug Administration in regulating nanomedical products. First, the FDA will have trouble fitting the products into the agency's classification scheme. Second, it will be difficult for the FDA to maintain adequate scientific expertise in the field. He concludes that the FDA should consider implementing several reforms now to ensure that it is adequately prepared to regulate nanomedicine.
Silver nanoparticles fabricated in Hepes buffer exhibit potent cytoprotective and post-infected anti-HIV-1 activities toward Hut/CCR5 cells.