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Mesoporous silica for drug delivery: Interactions with model fluorescent lipid vesicles and live cells
Abstract
Formulated mesoporous silica nanoparticle (MSN) systems offer the best possible drug delivery system through the release of drug molecules from the accessible pores. In the present investigation, steady state and time resolved fluorescence techniques along with the fluorescence imaging were applied to investigate the interactions of dye loaded MSN with fluorescent unilamellar vesicles and live cells. Here 1,2-dimyristoyl-sn-glycero-3-phospocholine (DMPC) was used to prepare Small Unilamellar Vesicles (SUVs) as the model membrane with fluorescent 1,6-diphenyl-1,3,5-hexatriene (DPH) molecule incorporated inside the lipid bilayer. The interaction of DPH incorporated DMPC membrane with Fluorescein loaded MSN lead to the release of Fluorescein (Fl) dye from the interior pores of MSN systems. The extent of release of Fl and spatial distribution of the DPH molecule has been explored by monitoring steady-state fluorescence intensity and fluorescence lifetime at physiological condition. To investigate the fate of drug molecule released from MSN, fluorescence anisotropy has been used. The drug delivery efficiency of the MSN as a carrier for doxorubicin (DOX), a fluorescent chemotherapeutic drug, has also been investigated at physiological conditions. The study gives a definite confirmation for high uptake and steady release of DOX in primary oral mucosal non-keratinized squamous cells in comparison to naked DOX treatment.
... In a model drug delivery study by Bardhan et al. on squamous cells showed that the amount of drug delivered to the cells by silica nanoparticles could be much higher compared to direct administration ( Figure 4) [22]. The implication of this could be in the effective reduction of the ED50 (effective dose) of a drug molecule with the help of silica nanoparticles. ...
... Sometimes the cargo itself may be tracked by visual stimulus. The mesoporous silica based nanomaterials [22,23] or the liposomes [30] that had been discussed earlier, all have the added advantage of imaging capability to them. An interesting and indirect use of nanomaterials in imaging has recently been highlighted in the literature [46], in which gels have been made by arranging silica nanoparticles on a glass slide covering them in a specialized biocompatible gelatin. ...
Nanomedicine is a booming field, however, the use of nanomaterials in medicine can be traced back thousands of years. Starting its journey in the dark ages of the gold ash in Indian traditional medicine through the Feynman’s futuristic concept of swallowing surgeon, the nanomedicine recently entered into the era of exponential growth. Due to the reduction in size, nanomaterials provide a unique advantage for application in biology. Like building a magic bullet for treating cancer or detecting disease, the use of nanoparticles is everywhere. In this chapter, we have discussed the current exciting developments in this field and what the future holds.
... pore sizes and particle morphology, in combination with large surface areas up to 1000 m 2 g À1 and tunable surface functionalities, are a few reasons for why this class of materials attracts extensive interest for use in drug delivery and tissue engineering applications. [3][4][5][6][7][8][9][10][11] The high inner surface area of the particles allows the loading with a large amount of active substance molecules. The synthesis of a variety of silica-based lms has been reported in literature, mainly by using evaporation-induced self-assembly in spin-or dipcoating, 12,13 or e.g. ...
Spatially and temporally controlled drug delivery is important for implant and tissue engineering applications, as the efficacy and bioavailability of the drug can be enhanced, and can also allow for drugging stem cells at different stages of development. Long-term drug delivery over weeks to months is however difficult to achieve, and coating of 3D surfaces or creating patterned surfaces is a challenge using coating techniques like spin- and dip-coating. In this study, mesoporous films consisting of SBA-15 particles grown onto silicon wafers using wet processing were evaluated as a scaffold for drug delivery. Films with various particle sizes (100 – 900 nm) and hence thicknesses were grown onto OTS-functionalized silicon wafers using a direct growth method. Precise patterning of the areas for film growth could be obtained by local removal of the OTS functionalization through laser ablation. The films were incubated with the model drug DiO, and murine myoblast cells (C2C12 cells) were seeded onto films with different particle sizes. Confocal laser scanning microscopy (CLSM) was used to study the cell growth, and a vinculin-mediated adherence of C2C12 cells on all films was verified. The successful loading of DiO into the films was confirmed by UV-vis and CLSM. It was observed that the drugs did not desorb from the particles during 24 hours in cell culture. During adherent growth on the films for 4 h, small amounts of DiO and separate particles were observed inside single cells. After 24 h, a larger number of particles and a strong DiO signal were recorded in the cells, indicating a particle mediated drug uptake. A substantial amount of DiO loaded particles were however attached on the substrate after 24 making the films attractive as a long-term reservoir for drugs on e.g. medical implants.<br
... Des nanoparticules de silice mésoporeuse ont ainsi été synthétisées en vue d'encapsuler des substances actives dans les années 2000 26 . Hautement fonctionnalisables et possédant une grande surface spécifique, elles ont été utilisées pour vectoriser divers types de substances et leurs applications ont été décrites en détail dans la litérature [27][28][29][30] . ...
La thérapie photodynamique (PDT), une thérapie basée sur l'irradiation de molécules photosensibilisatrices pour générer un stress oxydant, est déjà utilisée comme traitement de certaines pathologies. Très souvent, les photosensibilisateurs utilisés sont des molécules fortement hydrophobes qui s'agrègent en milieux aqueux. De ce fait, utilisées seules, elles nécessitent d'être injectées à des concentrations élevées, entraînant un risque de photosensibilisation générale. Pour diminuer cet effet secondaire et rendre le traitement plus efficace, il est possible d'encapsuler ces molécules. Des travaux précédant au sein du laboratoire des IRMCP ont permis le développement de vecteurs à base de copolymères à blocs pour l'encapsulation d'un photosensibilisateur, le phéophorbide-a. Ces travaux ont montré une efficacité de certains de ces vecteurs en conditions PDT sur des cultures cellulaires et ont ouvert des questions sur les processus de réponse cellulaire. L'objectif de ce doctorat était de développer des outils permettant de mieux comprendre les mécanismes ayant lieu lors de l'utilisation de nanovecteurs à base de copolymères à blocs encapsulant du phéophorbide-a et lors de l'irradiation lumineuse du photosensibilisateur. Les nanovecteurs étudiés étaient des micelles formulées à base de trois copolymères différents, le PEO-PCL, le PEO-PLA et le PEO-PS. Pour simplifier le système étudié, nous avons choisi d'utiliser des modèles de membranes pour simuler la cible biologique, des liposomes (ou vésicules lipidiques). En utilisant les propriétés de fluorescence du phéophorbide-a, nous avons pu obtenir les constantes d'affinité du photosensibilisateur pour les micelles et pour les vésicules lipidiques, puis évaluer le passage du phéophorbide-a des micelles vers les vésicules. Dans un second temps, nous nous sommes intéressés aux phénomènes en jeu lors de l'irradiation du photosensibilisateur. Nous avons pu estimer la production relative d'oxygène singulet en fonction du type de micelles utilisé. En suivant la fuite d'une sonde fluorescente contenue dans les liposomes, permettant ainsi de remonter à leur perméabilité, il a été possible mesurer les effets de la production d'oxygène singulet sur l'intégrité de la membrane des liposomes. De manière complémentaire, nous avons suivi l'oxydation des lipides constituant les liposomes durant l'irradiation du phéophorbide-a par spectrométrie de masse. Ces résultats combinés nous ont permis de voir quels étaient les paramètres influençant l'efficacité des micelles encapsulant un photosensibilisateur après irradiation et d'établir un classement de ceux ayant le plus d'effets sur l'intégrité de membranes modèles parmi ceux étudiés.
... pore sizes and particle morphology, in combination with large surface areas up to 1000 m 2 g À1 and tunable surface functionalities, are a few reasons for why this class of materials attracts extensive interest for use in drug delivery and tissue engineering applications. [3][4][5][6][7][8][9][10][11] The high inner surface area of the particles allows the loading with a large amount of active substance molecules. The synthesis of a variety of silica-based lms has been reported in literature, mainly by using evaporation-induced self-assembly in spin-or dipcoating, 12,13 or e.g. ...
Spatially and temporally controlled drug delivery is important for implant and tissue engineeringapplications, as the efficacy and bioavailability of the drug can be enhanced, and can also allow fordrugging stem cells at different stages of development. Long-term drug delivery over weeks to monthsis however difficult to achieve, and coating of 3D surfaces or creating patterned surfaces is a challengeusing coating techniques like spin- and dip-coating. In this study, mesoporousfilms consisting of SBA-15particles grown onto silicon wafers using wet processing were evaluated as a scaffold for drug delivery.Films with various particle sizes (100–900 nm) and hence thicknesses were grown ontotrichloro(octadecyl)silane-functionalized silicon wafers using a direct growth method. Precise patterningof the areas forfilm growth could be obtained by local removal of the OTS functionalization throughlaser ablation. Thefilms were incubated with the drug model 3,30-dioctadecyloxacarbocyanineperchlorate (DiO), and murine myoblast cells (C2C12 cells) were seeded ontofilms with different particlesizes. Confocal laser scanning microscopy (CLSM) was used to study the cell growth, and a vinculin-mediated adherence of C2C12 cells on allfilms was verified. The successful loading of DiO into thefilmswas confirmed by UV-vis and CLSM. It was observed that the drugs did not desorb from the particlesduring 24 hours in cell culture. During adherent growth on thefilms for 4 h, small amounts of DiO andseparate particles were observed inside single cells. After 24 h, a larger number of particles and a strongDiO signal were recorded in the cells, indicating a particle mediated drug uptake. The vast majority ofthe DiO-loaded particles remained attached to the substrate also after 24 h of incubation, making thefilms attractive as longer-term reservoirs for drugs one.g.medical implants.
... In the last decades, smart nanostructured materials have received numerous interests to improve drug delivery performance of classic administration routes [1][2][3] and maximize the therapeutic efficacy [4,5]. MSNs have recently been important parts of DDs due to their structural characteristics [6][7][8][9] such as; high physicochemical and biochemical stability [10], tunable mesopore size [11], biocompatibility [12], large surface areas and pore volumes [13]. But, some of their physicochemical properties have largely limited their biomedical applications [14,15]. ...
Drug delivery system (DDs) should include stimuli-responsive release at the target sites. With this goal, pH and Glutathione (GSH) microenvironment triggering mesoporous silica nanoparticles (MSNs) were prepared. In this system, the ZnO Quantum Dots, as a gatekeeper is bonded to the silica nanocarrier via a cleavable disulfide bond. ZnO QDs have the potential to be used as a gatekeeper due to, its acidic dissolution to Zn 2+ ions. Doxorubicin hydrochloride (Dox), an effective chemotherapeutic drug, is used to investigate the release behavior. Under physiological pH, ZnO QDs is stable, which resulted in blocked drugs inside the pores. Under the acidic pH, grafted ZnO QDs is removed due to its acidic dissolution, which resulted in the pore opening and releasing of the drug. Besides pH stimuli, the release of the drug was triggered by GSH.
... In the last decades, smart nanostructured materials have received numerous interests to improve drug delivery performance of classic administration routes [1][2][3] and maximize the therapeutic efficacy [4,5]. MSNs have recently been important parts of DDs due to their structural characteristics [6][7][8][9] such as; high physicochemical and biochemical stability [10], tunable mesopore size [11], biocompatibility [12], large surface areas and pore volumes [13]. But, some of their physicochemical properties have largely limited their biomedical applications [14,15]. ...
Drug delivery system (DDs) should include stimuli-responsive release at the target sites. With this goal, pH and Glutathione (GSH) microenvironment triggering mesoporous silica nanoparticles (MSNs) were prepared. In this system, the ZnO Quantum Dots, as a gatekeeper is bonded to the silica nanocarrier via a cleavable disulfide bond. ZnO QDs have the potential to be used as a gatekeeper due to, its acidic dissolution to Zn ²⁺ ions. Doxorubicin hydrochloride (Dox), an effective chemotherapeutic drug, is used to investigate the release behavior. Under physiological pH, ZnO QDs is stable, which resulted in blocked drugs inside the pores. Under the acidic pH, grafted ZnO QDs is removed due to its acidic dissolution, which resulted in the pore opening and releasing of the drug. Besides pH stimuli, the release of the drug was triggered by GSH.
Targeted drug delivery approaches have been widely employed to regulate the absorption and biodistribution of small molecules and biologics at the targeted diseased sites to maximize therapeutic performances without affecting the healthy cells of the tissue or organ inside the body. For this purpose, it is essential to select effective biomaterial-based platforms that can release drugs in a sustained manner without altering their bioactivity and causing toxic effects in off-targeted tissues. Such biomaterials can be directly implanted/injected into the targeted diseased area of the body to enhance drug delivery efficiency. Various materials have been explored to fabricate targeted drug delivery systems. Functional biomaterials with desired physicochemical and biological properties are getting colossal attention because they can respond to their environmental cues, such as fluctuations in pH, temperature, or cell-associated enzymatic activity, and improve drug delivery integration and tissue regeneration. This chapter explores the progress of different approaches in functionalizing polymeric, metallic, and ceramic biomaterials for targeted drug delivery systems.
This book on medical biotechnology offers a wide array of topics and cutting-edge research in the field featuring contributions from multiple authors, each specializing in their respective areas, making it highly valuable to science students and enthusiasts. The book provides a comprehensive coverage on a diverse range of topics, including sequence analysis, network pharmacology, drug discovery, CRISPR-Cas technology, precision medicine, neuroimaging biomarkers, therapeutics for neurodegenerative diseases, molecular pathogenesis of various diseases, plant-derived antioxidants, genetic approaches for disease diagnosis, cancer progression, immunotherapy, cancer biomarker identification, RNA Interference (RNAi), and nanotechnology in drug discovery and delivery, thus giving a holistic understanding of medical biotechnology.
Each chapter delves into the latest research and developments in its respective field, offering readers insights into cutting-edge advancements in medical biotechnology. This up-to-date information will be invaluable to science students and enthusiasts who want to stay at the forefront of the field.
The book adopts an interdisciplinary approach by incorporating elements of biology, genetics, computational techniques, nanotechnology, and more, thus, enables readers to see the interconnectedness of different scientific disciplines and how they contribute to medical biotechnology.
The book emphasizes practical applications, such as drug discovery, disease treatment, gene editing, and targeted drug delivery. This focus on real-world applications would be useful to readers interested in applying biotechnological techniques in the medical field. The book also acknowledges the serious challenges faced in the field of medical biotechnology and offers potential solutions to overcome these challenges to foster innovative thinking.
As a reader, you will gain a comprehensive understanding of various aspects of medical biotechnology, equipping you with knowledge that can contribute to technological breakthroughs, advancements in medicine, and the betterment of human life.
Abciximab (ABX) is a chimeric monoclonal antibody reported for antithrombotic activity but their delivery remains challenging due to its poor stability in a biological system. The purpose of this research was to deliver ABX on the target efficiently using mesoporous silica nanoparticles (MSN). ABX coated mesoporous silica nanoparticles (MSN-ABX) were formulated and analyzed for particle size, shape, zeta-potential, surface morphology and surface chemistry. XPS analysis confirmed the presence of ABX on the surface of amino functionalized mesoporous silica nanoparticles (MSN-NH2). The degree of ABX attachment was 67.53±5.81% which was demonstrated by the Bradford assay. Furthermore, the targeting efficiency of the targeted nanoparticles has been evaluated by capturing the fluorescent images in-vitro which showed the significant accumulation of the ABX coated nanoparticles towards activated platelets. The significant (P<0.05) increase in affinity of DiD dye loaded nanoparticles towards the activated platelets was confirmed by using an in-vitro imaging through photon imager optima. The hemolysis study of the nanoparticle formulations revealed that they were non-hemolytic for healthy human blood. The in-vitro antithrombotic effects of MSN-ABX were observed by blood clot assay which revealed its superior antithrombotic activity over clinical injection of ABX and could be a promising carrier for improved ABX targeted delivery.
Lung cancer is a leading cause of cancer-related death worldwide, with a very poor overall five-year survival rate. The intrinsic limitations associated with the conventional diagnosis and therapeutic strategies used for lung cancer have motivated the development of nanotechnology and nanomedicine approaches, in order to improve early diagnosis rate and develop more effective and safer therapeutic options for lung cancer. Cancer nanomedicines aim to individualize drug delivery, diagnosis, and therapy by tailoring them to each patient’s unique physiology and pathological features—on both the genomic and proteomic levels—and have attracted widespread attention in this field. Despite the successful application of nanomedicine techniques in lung cancer research, the clinical translation of nanomedicine approaches remains challenging due to the limited understanding of the interactions that occur between nanotechnology and biology, and the challenges posed by the toxicology, pharmacology, immunology, and large-scale manufacturing of nanoparticles. In this review, we highlight the progress and opportunities associated with nanomedicine use for lung cancer treatment and discuss the prospects of this field, together with the challenges associated with clinical translation.
Silica nanoparticles have rapidly found applications in medicine, supercapacitors, batteries, optical fibers and concrete materials, because silica nanoparticles have tunable physical, chemical, optical and mechanical properties. In most applications, high-purity silica comes from synthetic organic precursors, yet this approach could be costly, polluting and non-biocompatible. Alternatively, natural silica sources from biomass are often cheap and abundant, yet they contain impurities. Silica can be extracted from corn cob, coffee husk, rice husk, sugarcane bagasse and wheat husk wastes, which are often disposed of in rivers, lands and ponds. These wastes can be used to prepare homogenous silica nanoparticles. Here we review properties, preparation and applications of silica nanoparticles. Preparation includes chemical and biomass methods. Applications include biosensors, bioimaging, drug delivery and supercapacitors. In particular, to fight the COVID-19 pandemic,
recent research has shown that silver nanocluster/silica deposited on a mask reduces SARS-Cov-2 infectivity to zero.
Systematic delivery of therapeutic agents to specific sites, with a stimulus-responsive drug release profile is currently a rapidly growing area. Mesoporous silica nanoparticles (MSNs) are the useful platforms as drug/gene delivery systems due to their unique properties including the ability to control the pore size, high porosity, and morphology, which can directly affect the mechanism and profile of drug release. The appropriate fabrication strategy can tailor the particle shape and size, leading to enhanced delivery and release mechanisms. The MSN surface can be modified by using either organic or inorganic molecules to induce smart and site-specific drug delivery and release. Furthermore, application of molecules that function as pore gatekeepers with the ability to uncap via physiochemical stimuli can enhance the efficiency of drug delivery and release. This report aims to highlight the recent efforts and developments of strategies applied to render MSNs smarter and more effective for drug delivery applications.
As a novel member of the two-dimensional nanomaterial family, mono- or few-layer black phosphorus (BP) with direct bandgap and high charge carrier mobility is promising in many applications such as microelectronic devices, photoelectronic devices, energy technologies, and catalysis agents. Due to its benign elemental composition (phosphorus), large surface area, electronic/photonic performances, and chemical/biological activities, BP has also demonstrated a great potential in biomedical applications including biosensing, photothermal/photodynamic therapies, controlled drug releases, and antibacterial uses. The nature of the BP–bio interface is comprised of dynamic contacts between nanomaterials (NMs) and biological systems, where BP and the biological system interact. The physicochemical interactions at the nano–bio interface play a critical role in the biological effects of NMs. In this review, we discuss the interface in the context of BP as a nanomaterial and its unique physicochemical properties that may affect its biological effects. Herein, we comprehensively reviewed the recent studies on the interactions between BP and biomolecules, cells, and animals and summarized various cellular responses, inflammatory/immunological effects, as well as other biological outcomes of BP depending on its own physical properties, exposure routes, and biodistribution. In addition, we also discussed the environmental behaviors and potential risks on environmental organisms of BP. Based on accumulating knowledge on the BP–bio interfaces, this review also summarizes various safer-by-design strategies to change the physicochemical properties including chemical stability and nano–bio interactions, which are critical in tuning the biological behaviors of BP. The better understanding of the biological activity of BP at BP–bio interfaces and corresponding methods to overcome the challenges would promote its future exploration in terms of bringing this new nanomaterial to practical applications.
In this work, a pyridine containing Schiff-base, 1-((anthracen-10-yl)methylene)-2-(pyridin-2-yl)hydrazine (AP) and a pyrimidine containing Schiff-base 2-(2-(Anthracen-9-ylmethylene) hydrazinyl)-4, 6-dimethyl pyrimidine (ANHP) have been synthesized and characterized by IR, NMR, HRMS and different spectroscopic methods. Two different tri block co polymers (P-123 and F-127) have been used as delivering system of this poor water soluble drug molecule AP and ANHP which are the main investigation of this work. To find out which one is the better delivering systems of AP and ANHP, spectroscopic studies have been carried out in P-123 and F-127 polymeric media. From the interactions of AP and ANHP with P-123 and F-127 polymers individually, binding constant values have been determined. The drug delivering efficiency of block co polymers has been investigated by using different spectroscopic techniques like absorbance, fluorescence, DLS and time resolved fluorescence measurements. All these experimental results indicate that P-123 is the better AP and ANHP delivering system than F-127 polymer. In addition, the structural properties like bond length, bond angles etc. of AP have been calculated by using density functional theory (DFT).
Many bologically active water insoluble drug molecules have limited clinical applications because of strong hydrophobicity. Recently triblock copolymers have attracted enormous interests as potential drug carriers. For this purpose to deliver 5‐(1‐(bromohexa‐1,3,5‐triyn‐1‐yl)‐3a,4,5,6,7,7a‐hexahydro‐1H‐4,7‐methanoindazol‐3‐yl)‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbonitrile (PYZ) molecule, tri block copolymers are used. Before understanding the delivery of this water insoluble probe through triblock copolymers (TBP), solvent‐dependent fluorescence properties of this compound have been examined in different homogeneous solvents. Besides the experimental evidence, theoretical studies have also been done to explain actual orientation of atoms in PYZ molecule through optimized structures to support the experimental findings. Moreover, the three TBP polymers P‐123 (PEO19PPO69PEO19), F‐127 (PEO100PPO65PEO100) and L‐64 (PEO13PPO30PEO13) have been treated here as potential carriers encapsulating a pyrazoline derivative. The consequence of spatial captivity on the emission properties was systematically visualized by means of steady state and time resolved fluorescence spectroscopy. From DLS measurements the size variation with polydispersity index of TBP in presence and absence of PYZ in different triblock copolymers was also monitored. Furthermore these measurements have been supported by TEM imaging also.
Inorganic materials with short radiative decay time are highly desirable for fast optical sensors. This paper reports fast photoluminescence (PL) from a series of barium hexafluorosilicate (BaSiF6) superlong nanowires with high aspect ratios, codoped with Ce³⁺/Tb³⁺/Eu³⁺ ions, with subnanosecond decay time. Solvothermally synthesized BaSiF6 nanowires exhibit a uniform morphology, with an average diameter less than 40 nm and aspect ratios of over several hundreds, grown in c-axis direction with {110} surfaces. The PL emission from the codoped BaSiF6 nanowires, when excited by a 254 nm source, is dependent on Tb³⁺ concentration, and the energy transfer from Ce³⁺ to Tb³⁺ and to Eu³⁺ ions allows efficient emissions in the visible spectra when excited by a near UV source. Annealing BaSiF6 nanowires at 600 ○C in vacuum produced barium fluoride (BaF2) nanowires composed of nanocrystals. Both BaSiF6 and BaF2 nanowires exhibit fast emissions in the visible spectra, with enhanced intensities compared with their codoped microparticle counterparts. The decay time of codoped BaSiF6 nanowires is found to be shorter than that of codoped BaF2 nanowires. The energy transfer is also observed in their cathodoluminescence spectra with high-energy irradiation.
Natural cells have been explored as drug carriers for a long period. They have received growing interest as a promising drug delivery system (DDS) until recently along with the development of biology and medical science. The synthetic materials, either organic or inorganic, are found to be with more or less immunogenicity and/or toxicity. The cells and extracellular vesicles (EVs), are endogenous and thought to be much safer and friendlier. Furthermore, in view of their host attributes, they may achieve different biological effects and/or targeting specificity, which can meet the needs of personalized medicine as the next generation of DDS. In this review, we summarized the recent progress in cell or cell membrane-based DDS and their fabrication processes, unique properties and applications, including the whole cells, EVs and cell membrane coated nanoparticles. We expect the continuing development of this cell or cell membrane-based DDS will promote their clinic applications.
The acidification of various ligands was measured on a cell by cell basis for cell suspensions by correlated dual fluorescence flow cytometry. Mouse 3T3 cells were incubated with a mixture of fluorescein- and rhodamine-conjugated ligands, and the ratio of fluorescein and rhodamine fluorescence was used as a measure of endosome pH. The calibration of this ratio by both fluorometry and flow cytometry is described. Dual parameter histograms of average endosome pH per cell versus amount of internalization were calculated from this data, for samples in the absence and presence of chloroquine added to neutralize acidic cellular vesicles. The kinetics of acidification of insulin were measured and compared with previous results obtained with the chloroquine ratio technique. Rapid acidification of internalized ligand was observed both for insulin, which was mostly internalized via nonspecific pathways, and for alpha 2-macroglobulin, which was mainly internalized by specific receptor-mediated endocytosis. The average pH observed for internalized insulin was less than pH 6 within 10 min after addition of insulin. At 30 min, the average pH began to decrease to approximately pH 5, presumably because of fusion of endosomes with lysosomes.
The direct interaction of drugs with the cell membrane is often neglected when drug effects are studied. Systematic investigations are hindered by the complexity of the natural membrane and model membrane systems can offer a useful alternative. Here some examples are reviewed of how model membrane architectures including vesicles, Langmuir monolayers and solid supported membranes can be used to investigate the effects of drug molecules on the membrane structure, and how these interactions can translate into effects on embedded membrane proteins.
Functionalization of mesoporous silicananoparticles (MSNs) with Pd-porphyrins for cancer cell photodynamic therapy is reported. The composite platform, MSN–PdTPP, expands the role of Pd-porphyrins from their routine use as phosphorescence probes for oxygen sensing/imaging (diagnostics) to that of novel nano-photosensitizers for cancer cell phototherapy (therapeutics). The utility of MSN–PdTPP in the phototherapeutic treatment of MDA-MB-231 breast cancer cells is also evaluated, suggesting it is a promising cancer theranostic platform.
Molecular dynamics simulations have been used to determine the diffusion of water molecules as a function of their position in a fully hydrated freestanding 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) bilayer membrane at 303 K and 1 atm. The diffusion rate of water in a ∼10 Å thick layer just outside the membrane surface is reduced on average by a factor of ∼2 relative to bulk. For water molecules penetrating deeper into the membrane, there is an increasing reduction in the average diffusion rate with up to one order of magnitude decrease for those deepest in the membrane. A comparison with the diffusion rate of selected atoms in the lipid molecules shows that ∼6 water molecules per lipid molecule move on the same time scale as the lipids and may therefore be considered to be tightly bound to them. The quasielastic neutron scattering functions for water and selected atoms in the lipid molecule have been simulated and compared to observed quasielastic neutron scattering spectra from single-supported bilayer DMPC membranes.
Hollow spherical nanoparticles with ordered mesoporous silica shells were fabricated by evaporation-induced self-assembly using (NH(4))(2)SO(4) and cetyltrimethyl ammonium bromide (CTAB) as templates. The model drug, L-methionine, was encapsulated within the spherical void at high loadings by repeated crystallization.
The relationship between the conditions of membrane labelling by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) and its fluorescence parameters was investigated. In the labelling solutions prepared by the usual method, the presence of DPH microcrystals was revealed which led to the lower resultant fluorescence anisotropy values. Lower labelling efficiency was observed with DPH solutions in tetrahydrofuran when compared with solutions in acetone. Modifications of the labelling procedure are proposed which give better reproducibility of the results. There modified method involves the preparation of a 2 X 10(-4) mol. 1(-1) DPH stock solution in acetone, a 100-fold dilution in an appropriate buffer, subsequent bubbling through with nitrogen for 30 min and mixing the resulting solution with cell/membrane suspension in a 1:1 (v/v) ratio. Changes in intensity, anisotropy and spectra of DPH fluorescence in the course of membrane labelling were studied. A two-stage model of the incorporation of DPH into membranes was proposed, according to which DPH molecules first quickly adhere to the membrane surface and then are slowly translocated to the apolar regions of the membrane.
The acidification of various ligands was measured on a cell by cell basis for cell suspensions by correlated dual fluorescence flow cytometry. Mouse 3T3 cells were incubated with a mixture of fluorescein- and rhodamine-conjugated ligands, and the ratio of fluorescein and rhodamine fluorescence was used as a measure of endosome pH. The calibration of this ratio by both fluorometry and flow cytometry is described. Dual parameter histograms of average endosome pH per cell versus amount of internalization were calculated from this data, for samples in the absence and presence of chloroquine added to neutralize acidic cellular vesicles. The kinetics of acidification of insulin were measured and compared with previous results obtained with the chloroquine ratio technique. Rapid acidification of internalized ligand was observed both for insulin, which was mostly internalized via nonspecific pathways, and for alpha 2-macroglobulin, which was mainly internalized by specific receptor-mediated endocytosis. The average pH observed for internalized insulin was less than pH 6 within 10 min after addition of insulin. At 30 min, the average pH began to decrease to approximately pH 5, presumably because of fusion of endosomes with lysosomes.
The computer molecular modeling program HINT (Hydropathic INTeractions), an empirical hydropathic force field function that
includes hydrogen bonding, coulombic and hydrophobic terms, was used to study sequence-selective doxorubicin binding/intercalation
in the 64 unique CAxy, CGxy, TAxy, TGxy base pair quartet combinations. The CAAT quartet sequence is shown to have the highest
binding score of the 64 combinations. Of the two regularly alternating polynucleotides, d(CGCGCG)2 and d(TATATA)2, the HINT calculated binding scores reveal doxorubicin binds preferentially to d(TATATA)2. Although interactions of the chromophore with the DNA base pairs defining the intercalation site [I−1] [I+1] and the neighboring [I+2] base pair are predominant, the results obtained with HINT indicate that the base pair [I+3] contributes significantly to the sequence selectivity of doxorubicin by providing an additional hydrogen bonding opportunity
for the N3′ ammonium of the daunosamine sugar moiety in ∼25% of the sequences. This observation, that interactions involving
a base pair [I+3] distal to the intercalation site play a significant role in stabilizing/destabilizing the intercalation of doxorubicin into
the various DNA sequences, has not been previously reported. In general terms, this work shows that molecular modeling and
careful analysis of molecular interactions can have a significant role in designing and evaluating nucleotides and antineoplastic
agents.
Living systems exhibit form and function on multiple length scales and at multiple locations. In order to mimic such natural structures, it is necessary to develop efficient strategies for assembling hierarchical materials. Conventional photolithography, although ubiquitous in the fabrication of microelectronics and microelectromechanical systems, is impractical for defining feature sizes below 0.1 micrometres and poorly suited to pattern chemical functionality. Recently, so-called 'soft' lithographic approaches have been combined with surfactant and particulate templating procedures to create materials with multiple levels of structural order. But the materials thus formed have been limited primarily to oxides with no specific functionality, and the associated processing times have ranged from hours to days. Here, using a self-assembling 'ink' we combine silica-surfactant self-assembly with three rapid printing procedures--pen lithography, ink-jet printing, and dip-coating of patterned self-assembled monolayers--to form functional, hierarchically organized structures in seconds. The rapid-prototyping procedures we describe are simple, employ readily available equipment, and provide a link between computer-aided design and self-assembled nanostructures. We expect that the ability to form arbitrary functional designs on arbitrary surfaces will be of practical importance for directly writing sensor arrays and fluidic or photonic systems.
An optical imaging probe was synthesized by attaching a near-infrared carbocyanine fluorophore to an affinity group containing two zinc(II) dipicolylamine (Zn-DPA) units. The probe has a strong and selective affinity for the surfaces of bacteria, and it was used to image infections of Gram-positive S. aureus and Gram-negative E. coli bacteria in living nude mice. After intravenous injection, the probe selectively accumulates at the sites of localized bacterial infections in the thigh muscles of the mice.
Use of functionalized MCM‐41 solids as anion sensing systems has been demonstrated for the first time. The combination of the binding properties of molecular receptors with the structural characteristics of solid, inorganic surfaces leads to remarkably enhanced anion sensing response. The Figure shows a schematic view of a solid surface, with 300 Å diameter holes that are filled with aminoanthracene molecules.
Capsaicin is an ingredient of a wide variety of red peppers and it has various pharmacological and biological applications. The present study explores the interaction of capsaicin with dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane by monitoring various photophysical parameters using its intrinsic fluorescence. In order to have a clearer understanding of the photophysical responses of capsaicin, studies involving (i) its solvation behaviour in different solvents, (ii) the partition coefficient of capsaicin in different thermotropic phase states of lipid bilayer membrane and (iii) its location inside lipid bilayer membrane have been carried out. Capsaicin has a reasonably high partition coefficient for DMPC liposome membrane, both in solid gel (2.8 ± 0.1 x 105) and liquid crystalline (2.6 ± 0.1 x 105) phases. Fluorescence quenching study using cetylpyridinium chloride (CPC) as quencher suggests that the phenolic group of capsaicin molecule is generally present near the head group region and hydrophobic tail present inside hydrophobic core region of the lipid bilayer membrane. The intrinsic fluorescence intensity and lifetime of capsaicin sensitively respond to the temperature dependent phase changes of liposome membrane. Above 15 mol%, capsaicin in the aqueous liposome suspension medium lowers the thermotropic phase transition temperature by about 3 oC and above 30 mol%, the integrity of the membrane is significantly lost.
Doxorubicin (DOX) is an important anthracycline antibiotic whose intricate features of binding to DNAs, not yet fully understood, have been the object of intense debate. The dimerization equilibrium has been studied at pH = 7.0, I = 2.5 mM and T = 25ºC. A thermodynamic and kinetic study of the binding of doxorubicin to DNA, carried out by circular dichroism, viscometry, differential scanning calorimetry, fluorescence, isothermal titration calorimetry, and T-jump relaxation measurements, has enabled us to characterize for the first time two different types of ctDNA/DOX complexes, PD1 for CDOX/CDNA < 0.3, and PD2 for higher drug content. The nature of the PD1 complex is described better in light of the affinity of DOX with the synthetic copolymers [poly(dA-dT)]2 and [poly(dG-dC)]2. The formation of PD1 has been categorized kinetically as a two-step mechanism in which the fast step is the groove binding in the AT region and the slow step is the intercalation into the GC region. This bifunctional nature provides a plausible explanation for the high PD1 constant obtained (K1 = 5.7×108 M-1). Moreover, the formation of an external aggregate complex ctDNA/DOX (PD2) at the expense of PD1, with K2 = 9×105 M-1, has been evinced.
Membrane microdomains (rafts) remain one of the controversial issues in biophysics. Fluorescent molecular probes, which make these lipid nanostructures visible through optical techniques, are one of the tools currently used to study lipid rafts. The most common are lipophilic fluorescent probes that partition specifically into liquid ordered or liquid disordered phase. Their partition depends on the lipid composition of a given phase, which complicates their use in cellular membranes. A second class of probes is based on environment-sensitive dyes, which partition into both phases, but stain them by different fluorescence color, intensity, or lifetime. These probes can directly address the properties of each separate phase, but their cellular applications are still limited. The present review focuses on summarizing the current state in the field of developing and applying fluorescent molecular probes to study lipid rafts. We highlight an urgent need to develop new probes, specifically adapted for cell plasma membranes and compatible with modern fluorescence microscopy techniques to push the understanding of membrane microdomains forward.
On the basis of amino group-functionalized mesoporous materials, a pH-responsive system by constructing a designable coordination bonding-based "NH2-metal-DOX" architecture in mesopores has been investigated. The DOX can be released by the cleavage of either the "NH2-metal" or the "metal-DOX" coordinate bonding in response to pH variations. Here, the strengths of coordination bondings on both sides have been designed and fabricated from the aspects of NH2 loading amount, metal ion, and the counteranion accompanying the metal ion. It has been found that (i) the increase of amino group loading led to increased release percentage of the DOX under physiological condition due to a small number of "metal-DOX" bondings resulted from too many "NH2-metal" bondings, and this tendency finally resulted in a decrease in its stability; (8) the pH-sensitivity can be controlled by choosing the type of metal ion; and (iii) the physiological stabilities of "NH2-metal-DOX" architectures formed by various metal sources are in the decreasing order of CH3COO- > NO32- > SO42- > Cl-, indicating that different counteranions gave rise to different coordination bonding strengths of the architectures. Amino group loading amount of 24 mmol/g and CH3COO- counterion were suitable for "NH2-Zn-DOX" pH responsive delivery system, which was stable under physiological condition, while it was unstable with the DOX release triggered by the slight decrease to pH 6.0-5.0. The efficient cellular uptake of this pH-responsive system for cancer cells has been confirmed by cell assay. This coordination bonding-based pH-responsive system provides a new insight into the molecular factors governing the strength of chemical bonds in restrictive domain, which would open up new possibilities of porous materials for advanced applications in adsorption and desorption of biological and paramedical materials for antitumor therapy.
The pH-responsive delivery of an anti-cancer drug, MX, has been successfully achieved by varying the strength of the electrostatic interaction between the negatively charged silicate and positively charged MX, using MSN.
The potential use of functionalized MCM-41 solids as anion sensing systems was discussed. It was found that the anion sensing response was remarkably enhanced by combining the binding properties of molecular receptors with the structural characteristics of solid, inorganic surfaces. The analysis suggested that MCM-41 solids were suitable for the development of new generation of organic-inorganic hybrid nano-to micro-sized receptors for anion determination.
Optically clear thin mesoporous films with covalently attached
fluorescein entities are shown to exhibit very fast response pH
sensing.
Fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH) was found to be bicomponental in lipid bilayers and isotropic solvents. Mean lifetime values of both components correlated with the permittivity of the solvents. Decomposition of time-resolved spectra of DPH in phospholipid vesicles revealed a significant red shift of the spectrum of the short-lived component with respect to the spectrum of the long-lived component. This indicated that part of DPH was in a hydrophilic environment, which was supported by fluorescence energy transfer experiments. We showed that the increased fraction of the short-lived component in lipid bilayers originates from the population of DPH at the membrane–water interface.
Herein, we report a core–shell pH-responsive drug-carrier based on chitosan-coated mesoporous silica nanospheres. The efficient positively charged polymer (chitosan) coating is realized by the phosphoramidate covalent bonding between phosphonate groups on the surface of the mesoporous silica nanoparticles (MSNs) and amino groups on chitosan. A pH-responsive release of ibuprofen has been achieved by varying the shell structure of positively charged chitosan in the designed pH 4.0–7.4 solution. Under basic conditions, chitosan forms a gel like structure which is insoluble and hence prevents ibuprofen release at pH 7.4. When the pH is below its PI (6.3), the drug has been released due to protonation of the amino group on chitosan. These results imply that the chitosan coated-MSNs are promising platforms to construct pH-responsive controlled drug delivery systems.
The cooperative self-assembly of silica species and cationic surfactant cetyltrimethylammonium chloride (CTA+Cl− or CTAC) and the formation of mesoporous silica nanoparticles occur following the hydrolysis and condensation of silica precursor TEOS in the solution. The particle size can be controlled from 25 nm to 200 nm by adding suitable additive agents (e.g., inorganic bases, alcohols) which affect the hydrolysis and condensation of silica species. The in situ pH measurement of synthesis system is introduced to investigate the formation process of mesoporous silica nanoparticles. Our results show that a certain acid−base buffer capacity of the reaction mixture in a range of pH 6−10 is essential for the formation of mesoporous silica nanoparticles in the TEOS−CTA+ system. The nucleation and growth process of the nanoparticles can be extended into the self-assembly system of inorganic−surfactant and the formation of mesophase in aqueous media.
A new application of MCM-41 mesoporous materials has been developed. Two kinds of surfactants, C16TAB and C12TAB, have been employed to get different pore sizes. The samples were disk-shaped conformed before and after charging with ibuprofen, an anti-inflammatory drug. In all the cases the weight percent ratio of drug/MCM-41 was 30%. The drug release plots show a different behavior depending on the method for charging the drug in the material but not on the employed surfactant.
Membranes constitute a meeting point for lipids and proteins. Not only do they define the entity of cells and cytosolic organelles but they also display a wide variety of important functions previously ascribed to the activity of proteins alone. Indeed, lipids have commonly been considered a mere support for the transient or permanent association of membrane proteins, while acting as a selective cell/organelle barrier. However, mounting evidence demonstrates that lipids themselves regulate the location and activity of many membrane proteins, as well as defining membrane microdomains that serve as spatio-temporal platforms for interacting signalling proteins. Membrane lipids are crucial in the fission and fusion of lipid bilayers and they also act as sensors to control environmental or physiological conditions. Lipids and lipid structures participate directly as messengers or regulators of signal transduction. Moreover, their alteration has been associated with the development of numerous diseases. Proteins can interact with membranes through lipid co-/post-translational modifications, and electrostatic and hydrophobic interactions, van der Waals forces and hydrogen bonding are all involved in the associations among membrane proteins and lipids. The present study reviews these interactions from the molecular and biomedical point of view, and the effects of their modulation on the physiological activity of cells, the aetiology of human diseases and the design of clinical drugs. In fact, the influence of lipids on protein function is reflected in the possibility to use these molecular species as targets for therapies against cancer, obesity, neurodegenerative disorders, cardiovascular pathologies and other diseases, using a new approach called membrane-lipid therapy.
Three ordered mesoporous silica systems (OMS) were synthesized within the channels (120–200 nm in diameter, 60 μm long) of anodic alumina membranes (AAMs), i.e., systems (i) and (ii) with pore diameters of about 4 and 6 nm having a columnar alignment of mesopores and system (iii) featuring 6 nm pores arranged in a circular structure. These model systems allow one to eliminate the effect of particle size and particle morphology of the OMS, by using systems without significant external surface.Ibuprofen, an anti-inflammatory drug, was incorporated into these OMS–AAM systems by diffusion from solution. Uptake results showed that the included OMS increases the drug adsorption capacity with respect to the AAM as such. The highest uptake values were reached in the columnar OMS–AAM system with the larger pore diameter. The circular system, having similar structural parameters as the columnar one, i.e. pore size, pore volume and nitrogen surface area, showed the lowest adsorption capacity toward ibuprofen. The low accessibility of circular mesopores through defects creates a significant diffusion resistance for the ibuprofen molecules, thus showing that pore morphology strongly influences molecular diffusion.Drug release in a time window ranging from minutes to weeks was studied in a simulated body fluid (SBF). Concerning the columnar samples, the drug release rate decreased upon reducing the pore diameter. From the circular sample the ibuprofen was released with fast kinetics; it is proposed that the drug did not deeply diffuse into the structure. Nearly 30% of the total amount adsorbed was retained in the circular sample. Furthermore, after about a day the precipitation of hydroxyapatite precursors was detected on the surface of the mesoporous host, showing that the OMS–AAM system exhibits a “bioactive” behavior. This implies that after prolonged release times the diffusion of the drug out of the system can be slowed down through partial pore blocking.
We synthesized mesoporous silica nanoparticles (MSN) with different densities of surface positive charges. The positive surface charge was generated by incorporating trimethylammonium (TA) functional groups into the framework of MSN (MSN–TA) via direct co-condensation of a TA-silane and tetraethoxysilane (TEOS) in the presence of a base as a catalyst. These MSN–TA samples have well-defined hexagonal structures with an average particle diameter of 100 nm, pore size of 2.7 nm, and surface area of about 1000 m2 g−1. Anionic drug molecules, Orange II (a fluorescent tracing molecule), and sulfasalazine (an anti-inflammatory prodrug used for bowel disease), were effectively loaded into these MSN–TA samples and remained inside of the MSN–TA under acidic environment (pH 2–5). The amounts of loading of both Orange II and sulfasalazine were increased with increasing positive charge densities resulting from the increasing number of TA groups. When these drug-loaded MSN–TA nanoparticles were placed in physiological buffer solution (pH 7.4), a partial negative surface charge on the MSN–TA was generated due to the deprotonation of silanol groups, and the strong electrostatic repulsion triggered a sustained release of the loaded molecules. MSN–TA as a nanovehicle for pH-dependent loading and controllable release of anionic drug molecules can be used as an oral delivery drug systems targeting at intestine. These drugs can be remained trapped in the nanovehicle when passing through the stomach's acidic environment and be released in intestine where the environmental pH is close to neutral.
Although fluorescein is a widely used fluorescent probe in the biosciences, the effect of solvent environment on its spectral properties is poorly understood. In this paper we explore the use of fluorescein as a probe of the state of hydrogen bonding in its local environment. This application is based on the observation, originally made by Martin (Chem. Phys. Lett. 35, 105–111, 1975), that the absorption maximum of fluorescein undergoes substantial shifts in organic solvents related to the hydrogen bonding power of the solvents. We have extended this work by studying the spectral properties of the dianion form of the probe in solvent–water mixtures. We show that the magnitude of the shift correlates with the α and β parameters of Kamlet and Taft (J. Am. Chem. Soc. 98, 377–383; 2886–2894, 1976), which provide a scale of the hydrogen bond donor acidities and acceptor basicities, respectively, of the solvents. In solvent–water mixtures, these shifts reflect general effects of the solvents on the hydrogen bonding environment of the fluorescein through water–solvent hydrogen bonding and specific effects due to fluorescein–solvent hydrogen bonding. Indeed, both the absorption and fluorescence properties appear to be dominated by these effects indicating that the spectral shifts of the dianion can be used as an indicator of its hydrogen bonding environment. We discuss the application of fluorescein as a probe of hydrogen bonding in the microenvironment immediately surrounding the fluorophore, and we illustrate the effect with reference to the fluorescein–antifluorescein antibody complex where it appears that antibodies selected during the immune response possess binding sites that are increasingly dehydrated and hydrophobic.
The synthesis of mesoporous silica nanoparticles (MSN) covalently encapsulating fluoresceine or a photosensitizer, functionalized with galactose on the surface is described. Confocal microscopy experiments demonstrated that the uptake of galactose-functionalized MSN by colorectal cancer cells was mediated by galactose receptors leading to the accumulation of the nanoparticles in the endosomal and lysosomal compartments. The MSN functionalized with a photosensitizer and galactose were loaded with the anti-cancer drug camptothecin. Those MSN combining drug delivery and photodynamic therapy were tested on three cancer cell lines and showed a dramatic enhancement of cancer cell death compared to separate treatments.
The interaction between xanthene dye Fluorescein (Fl) and zinc oxide (ZnO) nanoparticles is investigated under physiological conditions. From the analysis of the steady state and time resolved spectroscopic studies in aqueous solution static mode is found to be responsible in the mechanism of fluorescence quenching of the dye Fl in presence of ZnO. ZnO nanoparticles are used as photocatalyst in order to degrade Fl dye. At pH 7, a maximum degradation efficiency of 44.4% of the dye has been achieved in presence of ZnO as a nanophotocatalyst and the photodegradation follows second-order kinetics.
Encapsulation of drugs within nanocarriers that selectively target malignant cells promises to mitigate side effects of conventional chemotherapy and to enable delivery of the unique drug combinations needed for personalized medicine. To realize this potential, however, targeted nanocarriers must simultaneously overcome multiple challenges, including specificity, stability and a high capacity for disparate cargos. Here we report porous nanoparticle-supported lipid bilayers (protocells) that synergistically combine properties of liposomes and nanoporous particles. Protocells modified with a targeting peptide that binds to human hepatocellular carcinoma exhibit a 10,000-fold greater affinity for human hepatocellular carcinoma than for hepatocytes, endothelial cells or immune cells. Furthermore, protocells can be loaded with combinations of therapeutic (drugs, small interfering RNA and toxins) and diagnostic (quantum dots) agents and modified to promote endosomal escape and nuclear accumulation of selected cargos. The enormous capacity of the high-surface-area nanoporous core combined with the enhanced targeting efficacy enabled by the fluid supported lipid bilayer enable a single protocell loaded with a drug cocktail to kill a drug-resistant human hepatocellular carcinoma cell, representing a 10(6)-fold improvement over comparable liposomes.
Luminescent and mesoporous Eu(3+)/Tb(3+) doped calcium silicate microspheres (LMCS) were synthesized by using mesoporous silica spheres as the templates. The LMCS and drug-loaded samples were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, and photoluminescence (PL) spectra. The results reveal that the LMCS have uniform spherical morphology with a diameter around 400 nm and the mesopore size of 6 nm. The prepared samples exhibit little cytotoxicity at concentrations below 5 mg mL(-1) via MTT assay. In addition, drug storage/release properties of the LMCS were demonstrated for ibuprofen (IBU). The obtained LMCS can be used to encapsulate drugs and release them. Under excitation by UV light, the IBU-loaded samples still show the characteristic (5)D(0)-(7)F(1-3) emission lines of Eu(3+) and the characteristic (5)D(4)-(7)F(3-6) emission lines of Tb(3+). The PL intensity of Eu(3+) in the drug carrier system increases with the cumulative released amount of IBU, making the drug release able to be tracked or monitored by the change of luminescence of Eu(3+). The LMCS reported here with mesoporous structure, good biocompatibility and luminescent property can be a promising drug delivery carrier.
The synthesis of ultrasmall, well-dispersed, hollow siliceous spheres (HSSs) by using a block copolymer as the template and tetraethoxysilane as a silica source under acidic conditions is reported. After removing the surfactant core of as-synthesized, spherical, silica-coated block-copolymer micelles, HSSs with a uniform particle size of 24.7 nm, a cavity diameter of 11.7 nm, and a wall thickness of 6.5 nm are obtained. It is shown that by surface functionalization of HSSs with methyl groups during synthesis, HSSs can be further dispersed in solvents such as water or ethanol to form a stable sol. Moreover, the hollow cavities are accessible for further loading of functional components. In addition, it is demonstrated that HSSs possess superior endocytosis properties for HeLa cells compared to those of conventional mesoporous silica nanoparticles. A feasible and designable strategy for synthesizing novel well-dispersed hollow structures with ultrasmall diameters instead of conventional ordered mesostructures is provided. It is expected that HSSs may find broad applications in bionanotechnology, such as drug carriers, cell imaging, and targeted therapy.
The effect that monodisperse amorphous spherical silica particles of different sizes have on the viability of endothelial cells (EAHY926 cell line) is investigated. The results indicate that exposure to silica nanoparticles causes cytotoxic damage (as indicated by lactate dehydrogenase (LDH) release) and a decrease in cell survival (as determined by the tetrazolium reduction, MTT, assay) in the EAHY926 cell line in a dose-related manner. Concentrations leading to a 50% reduction in cell viability (TC(50)) for the smallest particles tested (14-, 15-, and 16-nm diameter) ranging from 33 to 47 microg cm(-2) of cell culture differ significantly from values assessed for the bigger nanoparticles: 89 and 254 microg cm(-2) (diameter of 19 and 60 nm, respectively). Two fine silica particles with diameters of 104 and 335 nm show very low cytotoxic response compared to nanometer-sized particles with TC(50) values of 1095 and 1087 microg cm(-2), respectively. The smaller particles also appear to affect the exposed cells faster with cell death (by necrosis) being observed within just a few hours. The surface area of the tested particles is an important parameter in determining the toxicity of monodisperse amorphous silica nanoparticles.
The relative fluorescence of fluorescein over the pH range 3-12 has been measured at 516 nm, with excitation at 489 nm. The relative fluorescence is essentially zero at pH 3, increases slowly between pH 4 and 5, rises rapidly between pH 6 and 7, reaches a maximum at pH 8, and remains constant at above pH 8. The curve of relative fluorescence as a function of pH lies somewhat above the corresponding curve describing the fraction of fluorescein present as the doubly charged anion, Fl(2-), indicating much weaker fluorescence of the singly charged anion, HFl(-), and very much weaker fluorescence by the neutral species, H(2)Fl. The fluorescence data have been used to calculate a value for the third dissociation constant. Because of the complexity of the system, one unknown dissociation constant and three (relative) fluorescence constants, a series of three variable regressions on the data was made. The final values were K(HFl) = 4.36 x 10(-7) (mu = 0.10) for the third dissociation constant and K(H(2)Fl) = 0.8; kappa(HFl) = 5.7; kappa(Fl) = 100.0 for the relative fluorescence constants.
We report a new strategy for coupling chromone to Fe3O4 nanoparticles. The chromone-Fe3O4 NP conjugate shows a dramatic increase in chromone solubility in cell culture medium from less than 2.5 to 633 microg/ml, leading to the enhanced chromone uptake by HeLa cells. Chromone can be released at low pH and as a result, the chromone-Fe3O4 conjugate is much more efficient in inhibiting the HeLa cell proliferation. Such chromone-Fe3O4 NPs are promising as a powerful multifunctional delivery system for both chromone-based diagnostic and therapeutic applications.
Multilamellar liposomes, from mixtures of unoxidized (control) and singlet oxygen oxidized phosphatidylcholine, were studied by steady-state fluorescence anisotropy and multifrequency phase fluorometry using 1,6-diphenyl-1,3,5-hexatriene (DPH) as fluorescent probe. Lifetime fluorescence decay of the DPH-labeled liposomes was analyzed either by a model of discrete exponential components and a model that assumes a continuous distribution of lifetime values. Increasing the oxidized phosphatidylcholine content in the liposomes, an increase of the membrane interior polarity and a decrease of membrane fluidity occurs which can be related to the hydroperoxide-lipids and double bonds conjugation, respectively.
Although fluorescein is a widely used fluorescent probe in the biosciences, the effect of solvent environment on its spectral properties is poorly understood. In this paper we explore the use of fluorescein as a probe of the state of hydrogen bonding in its local environment. This application is based on the observation, originally made by Martin (Chem. Phys. Lett. 35, 105-111, 1975), that the absorption maximum of fluorescein undergoes substantial shifts in organic solvents related to the hydrogen bonding power of the solvents. We have extended this work by studying the spectral properties of the dianion form of the probe in solvent-water mixtures. We show that the magnitude of the shift correlates with the alpha and beta parameters of Kamlet and Taft (J. Am. Chem. Soc. 98, 377-383; 2886-2894, 1976), which provide a scale of the hydrogen bond donor acidities and acceptor basicities, respectively, of the solvents. In solvent-water mixtures, these shifts reflect general effects of the solvents on the hydrogen bonding environment of the fluorescein through water-solvent hydrogen bonding and specific effects due to fluorescein-solvent hydrogen bonding. Indeed, both the absorption and fluorescence properties appear to be dominated by these effects indicating that the spectral shifts of the dianion can be used as an indicator of its hydrogen bonding environment. We discuss the application of fluorescein as a probe of hydrogen bonding in the microenvironment immediately surrounding the fluorophore, and we illustrate the effect with reference to the fluorescein-antifluorescein antibody complex where it appears that antibodies selected during the immune response possess binding sites that are increasingly dehydrated and hydrophobic.
Fluorescence measurements of 1,6-diphenyl-1,3,5-hexatriene (DPH) in large unilamellar phospholipid vesicles were performed to characterize the influence of the membrane physical properties on the short-lived lifetime component of the fluorescence decay. We have found that the short-lived component of DPH significantly shortens when the membrane undergoes a temperature-induced phase transition as it is known for the long-lived component of DPH. We induced membrane phase transitions also by alcohols, which are reported to be distributed different way in the membrane--ethanol close to the membrane-water interface and benzyl alcohol in the membrane core. A different effect of the respective alcohol on the short and long decay component was observed. Both the time-resolved fluorescence spectra of DPH taken during lipid vesicle staining and the lifetime dependences caused by changes of temperature and/or induced by the alcohols show that the short-lived fluorescence originates from the population of dye molecules distributed at the membrane-water interface.
The controlled fabrication of biocompatible devices made of lipid bilayers deposited onto flat solid supports presents interest as models of cell membranes as well as for their biotechnological applications. We report here on the formation of supported lipid bilayers on silica nanoparticles (nanoSLBs). The successive steps of the adsorption of lipid vesicles on nanoparticles and the formation of nanoSLBs are revealed in detail by cryotransmission electron microscopy (cryo-EM). The formation of nanoSLBs was achieved for liposomes with positive, neutral, and low net negative charge, while liposomes with a high net negative charge adsorbed to silica nanoparticles but did not rupture. The nanoSLBs were found to follow faithfully the surface contours of the particles, information yet unavailable for SLB formation on planar solid substrates.
(Figure Presented) Keeping drugs under control: Hydrothermally stable, hollow mesoporous silica spheres have a high drug storage capacity, and polyelectrolyte multilayers coated on the spheres act as a switch for drug release which is controlled by the pH or ionic strength of the release medium. The picture shows the release of ibuprofen (IBU) from spheres with and without coatings of sodium polystyrene sulfonate (PSS) and poly(allylamine hydrochloride) (PAH).
The local drug release system is considered to be an alternative to treat the bone infection. In this paper, well-ordered mesoporous bioactive glasses (MBG) with high specific surface area have been synthesized in aqueous solution by a two-step acid-catalyzed self-assembly process combined with hydrothermal treatment. Gentamicin was encapsulated into the MBG by adsorption method and in vitro release of gentamicin from MBG was performed in distilled water and modified simulated body fluid (SBF), respectively. The results showed that the amount of drug loading of MBG was three times more than that of conventional sol-gel 58S. The outcomes of drug release in distilled water and in SBF showed that M58S effectively decreased the initial burst. During the release period, gentamicin was released from the M58S at a much lower release rate as compared to that from 58S after soaking in distilled water and SBF. Furthermore, the drug release was sensitive to the pH and ionic concentration of the release medium suggesting possible controls of the release rate. In addition, in contrast to conventional sol-gel 58S, M58S had higher ability to induce hydroxyapatite (HAp) formation. Therefore, well-ordered mesoporous bioactive glasses might be used as a bioactive drug release system for preparation of bone implant materials.
Steroid derivatives bearing fluorescent groups such as anthracene, dansyl, deazaflavin, and pyrene attached to C6 were synthesized. These compounds are unique inhibitors of cytochrome P450 3A4 (CYP3A4) and display similar IC(50) values in the microM range for the CYP3A4 substrates midazolam, testosterone, and nifedipine. On binding to CYP3A4, the fluorescence of the dansyl, deazaflavin, and pyrene probes is quenched by photophysical interaction of the fluorophore with the heme. The addition of drug candidates with binding constants in the nM-microM range causes displacement of the probes from the active site, and hence leads to restoration of fluorescence. Accordingly, relative affinities of drug candidates to CYP3A4 can be easily and accurately determined by fluorescence measurements.
Amyloidogenesis is a characteristic feature of the 40 or so known protein deposition diseases, and accumulating evidence strongly suggests that self-association of misfolded proteins into either fibrils, protofibrils, or soluble oligomeric species is cytotoxic. The most likely mechanism for toxicity is through perturbation of membrane structure, leading to increased membrane permeability and eventual cell death. There have been a rather limited number of investigations of the interactions of amyloidogenic polypeptides and their aggregated states with membranes; these are briefly reviewed here. Amyloidogenic proteins discussed include A-beta from Alzheimer's disease, the prion protein, alpha-synuclein from Parkinson's disease, transthyretin (FAP, SSA amyloidosis), immunoglobulin light chains (primary (AL) amyloidosis), serum amyloid A (secondary (AA) amyloidosis), amylin or IAPP (Type 2 diabetes) and apolipoproteins. This review highlights the significant role played by fluorescence techniques in unraveling the nature of amyloid fibrils and their interactions and effects on membranes. Fluorescence spectroscopy is a valuable and versatile method for studying the complex mechanisms of protein aggregation, amyloid fibril formation and the interactions of amyloidogenic proteins with membranes. Commonly used fluorescent techniques include intrinsic and extrinsic fluorophores, fluorescent probes incorporated in the membrane, steady-state and lifetime measurements of fluorescence emission, fluorescence correlation spectroscopy, fluorescence anisotropy and polarization, fluorescence resonance energy transfer (FRET), fluorescence quenching, and fluorescence microscopy.
Research on mesoporous materials for biomedical purposes has experienced an outstanding increase during recent years. Since 2001, when MCM-41 was first proposed as drug-delivery system, silica-based materials, such as SBA-15 or MCM-48, and some metal-organic frameworks have been discussed as drug carriers and controlled-release systems. Mesoporous materials are intended for both systemic-delivery systems and implantable local-delivery devices. The latter application provides very promising possibilities in the field of bone-tissue repair because of the excellent behavior of these materials as bioceramics. This Minireview deals with the advances in this field by the control of the textural parameters, surface functionalization, and the synthesis of sophisticated stimuli-response systems.
In this review, we highlight the recent research developments of a series of surface-functionalized mesoporous silica nanoparticle (MSN) materials as efficient drug delivery carriers. The synthesis of this type of MSN materials is described along with the current methods for controlling the structural properties and chemical functionalization for biotechnological and biomedical applications. We summarized the advantages of using MSN for several drug delivery applications. The recent investigations of the biocompatibility of MSN in vitro are discussed. We also describe the exciting progress on using MSN to penetrate various cell membranes in animal and plant cells. The novel concept of gatekeeping is introduced and applied to the design of a variety of stimuli-responsive nanodevices. We envision that these MSN-based systems have a great potential for a variety of drug delivery applications, such as the site-specific delivery and intracellular controlled release of drugs, genes, and other therapeutic agents.
- M Vallet-Regí
- A Rámila
- R P Del Real
- J Pérez-Pariente
M. Vallet-Regí, A. Rámila, R.P. Del Real, J. Pérez-Pariente, A new property of MCM-41: drug delivery system, Chem. Mater. 13 (2001) 308-311.
Membranes: a meeting point for lipids, proteins and therapies
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- J M Gonzalez-Ros
- F M Goni
- P K J Kinnunen
- L Vigh
- L Sanchez-Magraner
- A M Fernandez
- X Busquests
- I Horvath
- G Barcelo-Coblijn
P.V. Escriba, J.M. Gonzalez-Ros, F.M. Goni, P.K.J. Kinnunen, L. Vigh, L. Sanchez-Magraner, A.M. Fernandez, X. Busquests, I. Horvath, G. Barcelo-Coblijn,
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(2008) 829-875.
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- P Yang
- P Ma
- D Yanga
- J Lin
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1873-1879.