Evaluating the cellular uptake and translocation of silver nanoparticles using in vitro models.
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Zhang, Fan, 1987-
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Nanoparticles (NPs) are used in a wide range of applications for various characteristics associated with their size and shape. This research evaluated silver nanoparticles (AgNPs) as a model NP system to evaluate uptake, translocation, and associated toxicity. This study investigated the influence of capping agents for AgNPs on the cellular uptake in two epithelial cell lines at realistic exposure levels. In addition, it also investigated the interaction between soluble proteins and modeled cell membraneusing giant unilamellar vesicles (GUVs) and supported lipid bilayers, at physiologically relevant protein concentrations. Further, we developed a three-dimensional (3D) organotypic lung model resembling in vivo conditions, and tracked the translocation of AgNPs across the modeled lung barrier. Results show that particular capping agent on a AgNP modulates the extent of cellular uptake into different cell lines. Among the three investigated capping agents, tannic-acid coating was most efficient in delivering AgNPs into cells. Although the amount of internalized silver varied, none of the tested AgNPs resulted in cytotoxicity. Additionally, soluble proteins such as bovine serum albumin, hemoglobin, lysozyme and fetal bovine serum could induce structural changes in GUVs due to non-specific protein adsorption onto lipid membranes. The minimum concentration of proteins required for the onset of adsorption, and the relative affinities of adsorption, were dependent on the vesicle charge and the dipolar characteristics of a protein. Furthermore, by engaging human bronchial epithelial cells, microvascular endothelial cells and macrophage-like cells into a tri-culture, 3D system the overall structure exhibited similar properties to the alveolar-capillary barrier. Tannic acid-AgNPs were tested as model NPs, and translocated through multiple cell layers at both 4°C and 37°C. Cytotoxicity of AgNPs in tri-culture was more potent than that monoculture or biculture. The active response from tri-culture was most physiological relevant due to secretion of pro-inflammatory markers by macrophage like cells. The overall study highlighted the important role of the physiochemical properties of AgNPs in their biological fate. The intrinsic proteins aid the cellular internalization of AgNPs by altering lipid membrane stability and permeability. Physiologically relevant in vitro models can be a reliable tool in the evaluation of transport and toxicity of NPs.