Curvature Effects on the Adsorption of Plasma Proteins to Polystyrene

The interaction of human serum proteins with nanoparticles is of concern due to the increasing exposure of humans to applications that involve nanomaterials that can ultimately enter the bloodstream. The inclusion of these highly curved surfaces in medical devices, drug delivery technology, diagnostic testing methods, and particles found in air pollution has increased the desire to understand the corresponding adsorption behavior of proteins.;The adsorption behavior of human serum albumin (HSA) was studied using various techniques to measure protein adsorption isotherms for polystyrene films and particles. The particles have curvature approaching the length-scale of protein molecules. Quartz crystal microgravimetry with dissipation monitoring (QCM/D) and dual polarization interferometry (DPI) were analytical tools used to measure the amount of mass adsorbed to the surface of polystyrene films. A solution depletion method was used to measure changes in concentration of bulk protein after exposure to polystyrene nanoparticles; this quantification was carried out using capillary electrophoresis. Several adsorption isotherm models were fit to the data to determine trends in key adsorption parameters as a function of curvature.;The model fits suggest that an increase in surface curvature results in a decrease in protein-protein interactions and adsorption affinity. The decrease in adsorption affinity is well supported in the literature for various proteins interacting with nanoparticles and nanotubes. The decrease in protein-protein interactions was measured by a dye-binding fluorescence assay for intermolecular beta-sheet and supported this finding. Structural changes upon adsorption on less curved surfaces were greater than on more curved surfaces and this result is also supported in the literature.;Protein exchangeability was studied by exposing polystyrene nanoparticles to a mixture of human serum albumin and immunoglobulin G (IgG), the first two proteins in the plasma protein Vroman effect. The amount of HSA and IgG adsorbed to the particles suggest that multi-layer adsorption of HSA occurred and that HSA exchangeability on more curved surfaces increased.