Biocompatible coatings for luminal and outer surfaces of small-caliber artificial grafts

Luminal and outer surfaces of small-caliber vascular grafts at an early implantation period may require completely opposite cellular responses: minimal cellular adhesion and fibrin formation for a luminal surface versus potent cellular adhesion and migration and matrix generation for an outer surface. Differentiated biocompatible design of luminal and outer surfaces into small-caliber artificial grafts may lead to successful healing. We molecularly designed photocurable extracellular matrices (ECMs): photocurable chondroitin sulfate (CS) and hyaluronic acid (HA) for the luminal surface coating and photocurable gelatin for the outer surface coating. All of them were partially derivatized with photodimerizable groups such as thymine, cinnamate, and coumarin groups and converted to produce water-insoluble gels upon ultraviolet irradiation. In vitro study showed that platelet adhesion on photogelled CS and HA was significantly reduced, whereas endothelial cells adhered well on photogelled gelatin. These materials were individually coated and photogelled onto respective surfaces of artificial grafts (inner diameter [ID], 5 mm). During acute-phase implantation into dogs for up to 1 week, minimal cell adhesion was observed on the luminal surface, which was uniformly covered by photogelled CS or HA. Heparin impregnation of photocured ECM reduced fibrin formation. On the other hand, enhanced tissue ingrowth was noted at the outer surface. Although these ECM-coated grafts need further improvement in molecular design and coating techniques, photocurable ECMs may contribute to successful healing and a high patency rate of small-caliber artificial grafts.