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

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.