Protein adsorption on the poly(L-lactic acid) surface modified by chitosan and its derivatives

Surface modification of biomaterials has been adopted over the years to improve their biocompatibility. In this study, aiming to promote hydrophilicity and to introduce natural recognition sites onto poly(L-lactic acid) (PLLA) films, chitosan and its derivatives, carboxymethyl chitosan(CMC) and N-methylene phosphonic chitosan (NPC), were used to modify the surface of PLLA films by an entrapment method. Radiolabeled (125I) proteins were used to measure the amount of protein adsorbed to PLLA surfaces. Fibronectin (Fn) was used to study the protein adsorption on the modified PLLA surfaces, including isotherm adsorption and adsorption kinetics of single protein, competitive adsorption of binary proteins system and serum multi-proteins and the desorption behavior in serum solution. The results showed that in the isotherm adsorption, Fn had a larger adsorption capacity on the CS-modified surface at lower concentrations, but had a high adsorption capacity at CMC-modified surface at higher concentrations. In the study of absorption kinetics, Fn had a fastest adsorption equilibrium and a highest equilibrium adsorption capacity at the CS-modified surface, while it was opposite at the PCS-modified surface. When BSA and serum were added, it had the greatest effect on the adsorption of Fn on the PCS-modified surface. After 6 hours soaking in the desorption study, Fn had reached desorption equilibrium on all the modified surfaces, which had different effects on the desorption rate and the remaining percentage of Fn.