Covalent bonding of collagen on poly(L-lactic acid) by gamma irradiation

Surface modification of a biodegradable polymer, poly(L-lactic acid) (PLLA), with an extracellular matrix molecule, collagen, has been carried out by covalent bonding to PLLA via gamma irradiation grafting with poly(acrylic acid) as a coupling agent. The grafting yield increased with the increase of gamma absorbed dose. A grafting yield of more than 7% for collagen type I grafting was obtained at 21 kGy dose. The grafting yield was dose dependent. X-ray photoelectron spectroscopy confirmed the presence of proteins on the grafted PLLA. Swelling experiments revealed a crosslinked structure in the grafted polymer, whereas in comparison non-treated PLLA is linear. Localisation of collagen using immunostaining showed high levels of collagen on the grafted PLLA, confirming that the grafted collagen in the PLLA was still biologically active. The presence of collagen epitopes on the surface, i.e. having reactivity of the antibody against collagen on the surface of the grafted PLLA, demonstrated that irradiation may alter the molecular weight of collagen but not the availability of active binding sites. These results indicate that the single-step procedure of grafting by gamma irradiation could provide a simple but efficient technique to modify the biocompatibity of a scaffold for tissue engineering. (C) 2003 Elsevier Science B.V. All rights reserved.