(28e) Serum Protein Interactions With Nanoscale Osteogenic Thin Films

The coating of biomaterials enhances their biocompatibility as implants. Binding serum proteins to the surface greatly facilitates the adhesion and proliferation of hosts cells on implanted biomaterials.  We have previously shown that protamine-based layer-by-layer (LbL) polyelectrolyte multilayer (PEM) nanoscale thin film surface coatings of biomaterials support osteoblast adhesion, proliferation, and differentiation during in vitro culture in the presence of fetal bovine serum (FBS).  The primary objective of the current studies is to determine the effect of binding specific protein components of FBS to protamine-based PEMs on the adhesion, proliferation, and differentiation of osteoblast cells.  LbL nanoscale PEM thin film coatings using charged polyelectrolyte (protamine sulfate and SPS) were made using the spraying method. The linear growth of these PEM thin films was monitored by UV-Vis spectroscopy and the adsorption of bovine serum protein (BSA) and mixed protein constituents of FBS to the surfaces of negatively-charged outer surface (PrS/SPS)n and positively-charged outer surface (PrS/SPS)n (PrS)1 PEMs was evaluated. The net negative outer charge (PrS/SPS)n PEMs demonstrated a higher BSA adsorption compared to (PrS/SPS)n (PrS)1 PEMs. The total UV-Vis absorbance decreased similarly when both formulations of PEMs were incubated in the mixed protein FBS solution.  These results suggest that negatively charged BSA may exchange with negatively charged SPS at the (PrS/SPS)n PEM surface.  In contrast, incubation of both PEM formulations in FBS may result in the diffusion of both PrS and SPS from the PEM into the bulk FBS solution resulting in alteration in the surface topography and enhanced cell adhesion.