Comparison Of Mineralized-Crystallization And Reversed-Crystallization In Constructing Collagen-Hydroxyapatite Bone Substitute Materials

Ideal bone substitute should have several essential properties: ( I ) osteoconductive, which is a scaffold that supports the ingrowth of new bone;(II) osteoinductive, which stimulate MSCs cells to differentiate to osteoblast;(III) osteogen, which are capable of forming bone;(IV) structural strength;(V )biocompatibility.As bone is mainly composed of HA nanocrystals and Col fibers, many researchers have prepared Col-HA bone graft, in which HA and Col was composited by mineralized-crystallization method. Objective:In this study, the structure of nature bone has been analyzed. About mineralizational bone matrix, we observed the crystallizing site of HA on collagen fiber, and improved the precipitational method.We constructed another kind of bone matrix with Col and HA through reversed-crystallization method. And then we summarized the physicochemical properties and Biocompatibility of both kinds of bone matrices (Mineralized-crystallized Col-HA bone matrix/ MC and reversed-crystallized Col-HA bone matrix/ RC). Materials and Methods:1. We constructed MC Col-HA bone matrix by mineralized crystallization;constructed RC Col-HA bone matrix by Reversed crystallization.2. The DSC and tension strength of both bone matrices were compared. The effect of cross-linking and the performance of mechanics could conclude from those experiences.3. Through SEM and H&E staining, the characters of both bone matrices"structure were analyzed.4. The difference of elements in both bone matrices was mensurated by ESCA and XRD. Those experiences have provided basic for the biological analysis and mechanic analysis.5. The MSCs has been seeded into both bone matrices for the comparison of biocompatibility.6. The effect of repairing bone defect was observed in vivo. Results:Physicochemical examination: The structure became irregular after HA is introduced into collagen matrix through both methods. The mechanical strength of matrices was decreased by the process of mineralized crystallization. Compared with RC bone matrix (0.69 MPa), the tension strength of MC bone matrix decreases significantly (0.21 MPa). The rupture length also decreases from 3.13% to 1.13%. And the transition temperature in DSC reduces from 109 °Cto 102 °C.Biocompatibility evaluation: There is significant difference (p=0.0194<0.05) between two groups at room temperate. The cell adhered and proliferated on the surface of RC bone matrix was much better then on MC bone matrix.Application of both matrices in repairing bone defect: Both bone matrices could repair bone defect in vivo at last. There was no significant difference between the groups. As for the repair rate, the RC bone matrix was much quicker then MC bone matrix. Conclusions:From all experiences, it could be concluded that both bone matrices could repair bone defect in vivo. By comparison with MC Col-HA bone matrix, the RC Col-HA bone matrix has much stronger intensity, much better biocompatibility. It could repair the bone defect in vivo much more quickly.