Physicochemical Interactions of Engineered Nanoparticles with Model Cell Membranes

Due to the widespread application of engineered nanoparticles (ENPs) and their potential release into the environment, it is important to assess their potential impacts on human health. Recent studies have shown that both carbon-based and inorganic ENPs can induce cytotoxicity toward human cells. An improved understanding of how ENPs interact with biological membranes will help elucidate the mechanisms for their cytotoxicity. In this dissertation, the physicochemical interactions of both carbon-based and inorganic nanoparticles with model cell membranes were investigated. The deposition of graphene oxide (GO) on supported lipid bilayers (SLBs) formed on silica surfaces was controlled by electrostatic interactions. Upon attachment of GO to supported lipid vesicles that were encapsulated with fluorescence dye, release of dye was detected, thus demonstrating that the vesicles were disrupted. The dye release was substantially reduced when the exposure of the vesicles to GO suspension was terminated, suggesting that the vesicles have a self-healing ability. The adsorption of human serum albumin (HSA) on GO was investigated through a combination of batch adsorption experiments and quartz crystal microbalance with dissipation (QCM-D) measurements. An increase in ionic strength under neutral pH conditions resulted in higher adsorption densities as well as more compact HSA layers on GO. The attachment of GO to SLBs was reduced in the presence of protein coronas, and the degree of reduction was influenced by the conformation of the adsorbed protein layers on GO. In a separate study, phosphate ions were shown to adsorb appreciably on alumina and ceria nanoparticles and impart additional negative charge to the particles. As a result, the attachment of these two nanoparticles to SLBs at neutral pH was considerably reduced in the presence of phosphate. In the third part of the dissertation, the interactions forces between silver nanoparticles (AgNPs) and SLBs were measured using an atomic force microscope (AFM). The AFM tips were functionalized with AgNPs by sequentially exposing the tips to polydopamine and silver nitrate solutions. The AFM force measurements revealed that AgNPs experience predominantly repulsive forces when approaching SLBs. The presence of HSA resulted in an enhancement in the repulsive interactions between AgNPs and SLBs likely through steric repulsion