Non-specific and specific interactions on functionalized polymer surface studied by FT-SPR

Fourier transform surface plasmon resonance (FT-SPR) was utilized to study specific and non-specific interactions between proteins and a biotinylated polymer film by monitoring adsorptions of streptavidin (SAv) and bovine serum albumin (BSA) on the polymer films. The biotinylated polymer, poly(lactide-co-2,2-dihydroxymethyl-propylene carbonate-graft-biotin) [P(LA-co-DHC/biotin)], was prepared by ring-opening copolymerization of lactide and a OH-bearing cyclic carbonate monomer, followed by biotinylation of the OH groups. The copolymer was coated onto the FT-SPR chip and vacuum-dried, hydrated at 70°C, and treated with a blocking agent respectively to achieve different surface status. The FT-SPR results showed that the vacuum-dried film had the most BSA adsorption; hydration treatment led to migration of the biotin moieties from inner film to surface and thus resulted in less BSA adsorption; blocking layer on the polymer surface saturated the active sites for physical and chemical adsorptions on the surface and thus weakened the BSA adsorption. Adsorption of SAv displayed similar polymer-surface-status dependence, i.e., more adsorption on vacuum-dried surface, less adsorption on hydrated surface and the least adsorption on blocked surface. Compared with BSA, SAv showed more enhanced adsorptions on P(LA-co-DHC/biotin) surface because of the specific interaction of biotin moieties in the polymer with SAv molecules, especially on the blocked surface. The above semi-quantified results further indicate that the FT-SPR system is suitable for investigating interactions between polymer surface and bio-molecules.