Endothelial cell attachment to the gamma irradiated small diameter polyurethane vascular grafts

Previously we have fabricated the small diameter polyurethane (Pellethane 2363-80A, abbreviated PU) vascular grafts that were modified by epoxy-crosslinked gelatin (abbreviated gelatin) and an RGD-containing protein (abbreviated CBD-RGD) to facilitate the endothelial cell (EC) seeding on the surface. In this study, the biocompatibility of such surface after freeze-drying and gamma irradiation was evaluated. The contact angle of the irradiated PU dropped a little and the ESCA spectra revealed oxygen bonding. The increases in the amount of extractables as well as in the molecular weight distribution were observed. The mechanical properties decreased only slightly. The irradiated PU surface showed enhanced EC affinity that persisted after several months of storage. Gelatin, CBD-RGD (used with either gelatin or PU), and PU modified by gelatin and CBD-RGD all demonstrated higher EC affinity after freeze-drying and gamma irradiation (2.5 Mrad). The positive cellular effect remained after storage. Based on these results, freeze-drying followed by gamma irradiation at 2.5 Mrad is a proper way to process and store these vascular grafts.