Evaluation of composition and crosslinking effects on collagen-based composite constructs

Vascular grafts are widely used for a number of medical treatments. Strength, compliance, endothelialization and availability are issues of most concern for vascular graft materials. With current approaches, these requirements are difficult to satisfy simultaneously. To explore an alternative approach, the present study has engineered the collagen gel construct by incorporating mimetic components and crosslinking the construct with different crosslinkers. The effects of component additives, such as chitosan and elastin, have been evaluated in terms of their mechanical and biological properties. Results demonstrate that the incorporation of chitosan and/or elastin alter stress–strain curves in the low stress loading region, and significantly improve the stretching ratio and ultimate stress of gel constructs compared to collagen constructs. Electron microscopy results suggest that the mechanical improvements might be due to microstructural modifications by chitosan sheets and elastin fibers. The effects of crosslinkers, such as formaldehyde, genipin and ethyl-(dimethyl aminopropyl) and carbodiimide hydrochloride (EDAC) have also been evaluated. Results demonstrate that formaldehyde, EDAC and genipin employ different mechanisms to crosslink collagen-based constructs, and use of genipin as a construct crosslinker exhibits improved elongation and endothelial coverage as compared to formaldehyde and EDAC. In addition, extending gelation time increased the elastic modulus but not the ultimate strength. Therefore, this study suggests that the mimicry of natural vessel tissues with properly crosslinked biopolymer composites could be a potential material design strategy for vascular graft materials.