Structural Changes of Bovine Serum Albumin upon Adsorption to Modified Fluoropolymer Substrates Used for Neural Cell Attachment Studies

In this work, we report changes in steady-state fluorescence spectra for dansylated bovine serum albumin (BSA) on its adsorption to a series of modified poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) surfaces. Specifically, dansylated BSA (BSA-Dan) is adsorbed to unmodified FEP, radio frequency glow discharge plasma modified FEP (resulting in an hydroxylated surface, FEP-OH), and FEP-OH that is subsequently treated with γ-(aminopropyl)triethoxysilane (resulting in an aminated surface). The emission spectra of the most strongly adsorbed BSA-Dan is red shifted (>45 nm) relative to native BSA-Dan. The emission spectrum of BSA-Dan adsorbed on amine-modified FEP is red shifted by an additional 15 nm relative to BSA-Dan adsorbed on unmodified FEP. These results suggest that the microenvironment surrounding the dansyl reporter group is altered significantly on BSA adsorption and the microenvironments are different for BSA-Dan adsorbed to the various FEP-based surfaces. The emission spectrum of BSA-Dan adsorbed to the amine-modified FEP surface resembled that of chemically denatured BSA-Dan on unmodified FEP. This is consistent with adsorption leading to a conformational change that is similar to the one induced by chemical denaturation. These results, suggesting conformational changes in the adsorbed BSA, provide insight into our previously published results showing selective cellular attachment of mouee neuroblastoma cells (NB2a) and rat endothelial cells onto the amine-modified FEP only in the presence of adsorbed BSA (J. Biomed. Mater. Res. 1993, 27, 917).