Covalent immobilization of chitosan/heparin complex with a photosensitive hetero-bifunctional crosslinking reagent on PLA surface.

Chitosan (CS) was covalently immobilized onto polylactic acid (PLA) film surface using the photosensitive hetero-bifunctional crosslinking reagent, 4-azidobenzoic acid, which was previously bonded to chitosan by reaction between an acid group of the crosslinking reagent and a free amino group of chitosan. The immobilization was accomplished by irradiating with ultraviolet light, the modified chitosan being coated on the film surface to photolyze azide groups, thus crosslinking chitosan and PLA together. The hydroxyl and amino groups of chitosan may provide the opportunity for them being further derived by chemically immobilizing a variety of functional groups. These modifications could be carried out to tailor PLA biomaterial to meet the specific needs of different biomedical applications. For example, chitosan molecules immobilized on the PLA could be modified by heparin (Hp) solution to form a polyelectrolyte complex on the PLA surface. Platelet adhesion assay showed that PLA surface modified by chitosan/heparin complex could inhibit platelet adhesion and activation. Cell culture assay indicated that PLA surface with CS/Hp complex showed enhanced cell adhesion.