Bio-inspired surface modification of biodegradable polymer substrates for endothelization

Abstract

We developed dual factor immobilization system using bio-inspired surface coating methods and applied them to prepare functionalized vascular graft materials based on poly(lactic acid-co-ɛ-caprolactone) (PLCL), the elastic and biodegradable polymer. The immobilized bioactive molecules included a RGD-containing peptide and basic fibroblast growth factor (bFGF) to enhance endothelialization. Through ELISA and fluorescamine assay, we found that polydopamine-layer was successfully formed on the surface PLCL substrate, which was used for immobilization of dual factors; the amount of bioactive molecules on the polydopamine-deposited PLCL film was increased in a time dependent manner. X-ray photoelectron spectrometer (XPS) confirmed that intensity of C-N peak was increased demonstrating successful immobilization of bioactive molecules on the developed surface. In cell test, the dual factor immobilized group showed the largest cell spreading area and recorded the highest cell numbers in proliferation test during 14 day culture. Endothelialization marker expression test, analyzed by Western blot and RT-PCR, presented that co-immobilized factors highly stimulated CD31 and vWF-1 expression. These data indicate the functionality of each molecule is maintained effectively due to polydopamine coating and immobilized factors can lead synergistic effects on HUVEC behaviors. Furthermore, we observed the enhanced expression level of CD31 on developed nanofiber substrate through immunostaining. This confirmation work suggests that the co-immobilization platform can be available with different bioactive molecules and our system will open the possibility of various approaches in tissue engineering field.