Surface modification of polycaprolactone substrates using collagen-conjugated poly(methacrylic acid) brushes for the regulation of cell proliferation and endothelialisation

Abstract

The incorporation and presentation of cell recognition ligands on the surfaces of biodegradable blood-vessel implants to promote endothelialisation is considered to be a promising approach to prevent platelet aggregation and hence thrombogenesis. In this study, cell-adhesive collagen was covalently immobilised onto polycaprolactone (PCL) substrates via surface-initiated atom transfer radical polymerization (ATRP) to improve cell–material interactions. Functional polymer brushes of poly(methacrylic acid) (P(MAA)) containing dense and reactive carboxyl groups (–COOH) were formed on the PCL substrates in a controllable manner. The amount of collagen, which was conjugated to the pendant carboxyl groups via carbodiimide chemistry, increased with the concentration of –COOH groups on the grafted P(MAA) brushes. The affinity and growth of endothelial cells (ECs) were found to be significantly improved on the collagen-immobilised PCL substrates, and this improvement is positively correlated with the amount of covalently conjugated collagen. Thus, surface-initiated ATRP provides an alternative methodology for the surface functionalisation of biodegradable polyester scaffolds to enable the formation of a confluent layer of ECs. An optimally endothelialised material surface will play a major role in the minimisation of thrombogenicity and inflammation, and hence can be potentially used for vascular graft applications.