Human Vascular Endothelial Growth Factor Or Platelet Derived Growth Factor-BB To Demineralized Bone Matrix Improve Angiogenesis

Functional biomaterials are bioactive materials which could affect biochemical and/or physiological process to promote tissue regenerations. Growth factors have been utilized to activate collagen biomaterials for their specific roles in promoting cell proliferation, movement and differentiation. However, simple absorption of growth factors to demineralized bone matrix (DBM) results limited repair effects for their rapid diffusion in vivo. In our study, we employed two methods, haperin mediating and direct chemical crosslinking, to immobilize VEGF and PDGF-BB on DBM respectively, which could promote tissue regenerations on implanted DBM.Heparin-crosslinked demineralized bone matrices (HC-DBM) pre-loaded with vascular endothelial growth factor (VEGF) were designed to promote cells and new microvessels invasion into the matrices. After chemically crosslinking of heparin, the DBM scaffold could specifically bind to VEGF and controlled, localized and sustained delivery of VEGF was achieved. The biological activity of VEGF on HC-DBM was demonstrated by promoting endothelial cells proliferation. Evaluation of the angiogenic potential of heparinized DBM loading with VEGF was further investigated by subcutaneous implantation. The significant angiogenesis of heparinized DBM loaded with VEGF was observed from haematoxylin-eosin (H.E.) staining and immunohistochemistry examination. The results demonstrated that heparin modified DBM combining with VEGF was a useful strategy to stimulate cells and blood vessels invasion of the scaffolds.The aim of the present work is to develop a chemical approach to immobilize the platelet derived growth factor-BB (PDGF-BB) on DBM with cross-linker reagents. The amount of PDGF-BB covalently immobilized on DBM was significantly increased, comparing to natural absorption. The increased proliferation of fibroblasts demonstrated that the biological activity of PDGF-BB was not significantly reduced by chemical crosslinking with sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (Sulfo-SMCC) and 2-iminothiolane·HCl (Traut's Reagent). The angiogenic potential of DBM crosslinked with PDGF-BB was further investigated by implanting the scaffolds into the dossal side of rats for 7 and 14 days. Comparing to the control groups, there was statistically significant increase of blood vessel density in PDGF-C-DBM group at both time points. These results clearly demonstrated that the conjugation efficiency of PDGF-BB on DBM was significant using Sulfo-SMCC and Traut's Reagent, and the surface bioactivity of the scaffolds on stimulation cell and new blood vessel invasion was improved. Thus, the direct chemical crosslinking approach could be used to effectively retain growth factors on the collagen based scaffolds to develop functional biomaterials.