Abstract
Centrifugation-based assays are commonly employed to study protein-membrane affinity or binding using lipid bilayer vesicles. An analogous assay has been developed to study nanoparticle-membrane interactions as a function of nanoparticle surface functionalization, membrane lipid composition, and monovalent salt concentration (NaCl). Anionic (carboxylic acid, Ag-COOH), cationic (amine, Ag-NH), and polyethylene glycol coated (Ag-PEG) silver nanoparticles (AgNPs) were examined based on their surface plasmon resonance (SPR), which was used to determine the degree of binding to anionic, cationic, and zwitterionic membrane vesicles by analyzing supernatant and sediment phases. SPR was also used to examine AgNP aggregation in solution and at membrane-water interfaces, and direct visualization of AgNP-membrane binding, vesicle aggregation, and vesicle disruption was achieved by cryogenic transmission electron microscopy (cryo-TEM). The extent of AgNP binding, based on AgNP + vesicle heteroaggregation, and vesicle disruption was dependent upon the degree of electrostatic attraction. Because of their biological and environmental relevance, Ag-PEG + anionic vesicles systems were examined in detail. Cryo-TEM image analysis was performed to determine apparent membrane-water partition coefficients and AgNP aggregation states (in solution and bound to membranes) as a function of NaCl concentration. Despite possessing a PEG coating and exhibiting a slight negative charge, Ag-PEG was able to bind to model anionic bacterial membranes either as individual AgNPs (low salt) or as AgNP aggregates (high salt). The centrifugation assay provides a rapid and straightforward way to screen nanoparticle-membrane interactions.
Highlights
The introduction of nanoparticles into biological processes leads to new challenges: (1) the characterization of the interaction between nanoparticles and cell membranes; (2) the evaluation of biocompatibility between nanoparticles and cell membranes; (3) the measurement of the cytotoxicity induced by nanoparticles and (4) the prediction of the impact of nanoparticles to biological systems
It has been studied that nanoparticles may introduce carcinogenic risks, which may be triggered by the production of reactive oxygen species (ROS) by macrophages attempting to destroy foreign materials on the inflammation sites
Interfacial interactions and the adhesive binding strength are based on nanoparticle surface functionalization and membrane lipid composition, and control the extent to which a nanoparticle will penetrate into the membrane and disrupt lipid organization and membrane structure.[1,2]
Summary
1.1 Nanoparticle - membrane interaction Over the past two decades, nanoparticles have been increasingly used for biological applications such as antimicrobial agents, therapeutics imaging, diagnosis and targeted drug / gene delivery.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33] For example, silver nanoparticles have been used for disinfection and creating antifouling surfaces.[22]. It has been observed that nanoparticles were able to bind to membrane, causing local changes in membrane curvature.[34,35,36,37] The extent of nanoparticle-induced biophysical and/or biochemical changes on cell membranes would be dependent on the size, charge, surface reactivity, surface chemistry and compositions of nanoparticles.[38,39,40,41,42] It has been studied that nanoparticles may introduce carcinogenic risks, which may be triggered by the production of reactive oxygen species (ROS) by macrophages attempting to destroy foreign materials on the inflammation sites. Given the importance of nanoparticle–membrane interactions in nanotoxicology and nanomedicine, and the vast range in nanoparticle composition, size, shape, and surface functionalization, there is a need to develop techniques that can rapidly and inexpensively analyze the membrane-activity of nanoparticles using free standing or unsupported membranes. Lipids act as a solvent for all the substances, facilitating their diffusion through the membrane
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