Preparation And Performance Of Spatial Controlled Distribution Of HACC In Mineralized Collagen Coatings

Coatings on metal implant should have good biological response capability and good capability on loading/release biological factors, so as to accelerate the osseointergration process. Limited by the thickness of the bioactive coating on mental implant, the biological factor loading/release capability of the coatings is not proper. In this study, based on the research finding that mineralized collagen coating possess good cytocompatibility and porous morphology, we take advantage of positively charged property of 2-Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) in broad pH range and its interaction between biological factors to incorporate HACC molecule into mineralized collagen coating. In order to avoid harmful effect of HACC to cells, we also controllably distributed HACC into different spaces of mineralized collagen coating. The loading amount and release behavior of biological factor as well as biological assessments of this novel coating were conducted, the main results were summarized as follows:HACC nanospheres were prepared through ionic gelation process and were co-deposited with mineralized collagen onto titanium plate by electrochemical deposition method. The preparation conditions of HACC nanospheres and the co-deposition behavior were investigated, the results showed that a large amount of free HACC molecules could not be separated from nanospheres, influencing nanospheres co-deposition with collagen.Compared to HACC nanospheres, HACC molecule alone could be more electric field sensitive and could be controllably distributed into different spaces of mineralized collagen coating. The results showed, (1) under negative potential, collagen and HACC could be deposited into coating. Under positive potential with relatively short deposition time, quantity of collagen coating could be improved and the deposited-low-mineralized HACC could be repelled from coating. Deposition time could also influence the thickness of coating and amount of deposited HACC. After three alternations of negative/positive potential depositions, the thickness of collagen coating could reach a suitable degree. (2) a small negative potential (-1.5V/60s) was applied as the pre-deposition to enrich HACC near Ti plate, and a positive potential was applied at the end of deposition, thus mineralized collagen coating with main HACC distributed in the inner part(HACC-IN) could be prepared. (3) followed by three alternations to accumulate a suitable thickness of mineralized collagen coating, a negative potential with long deposition time (-2.4V/480s) was applied, and thus mineralized collagen coating with main HACC distributed in the outer part(HACC-OUT) could be prepared.Biological assessment on HACC spatial-controlled mineralized collagen coatings were conducted. The rhBMP-2 loading capability of coatings could be significantly enhanced by the incorporation of HACC, with loading amount increased 41%. HACC-IN coatings could load rhBMP-2 deeper so as to inhibit explosive release at early stage and prolong release time up to 28 days. With HACC located in inner layer, HACC-IN coatings minimize the harmful effect of HACC, not only without compromise good compatibility of mineralized collagen coatings, but also improved their compatibility by protein absorption. The HACC spatial-controlled mineralized collagen coatings possessed good compatibility and loading/release ability, showed better cell differentiation and therefore could accelerate bone healing process.