Enhanced Drug/Growth Factor Loading And Release Ability Of Mineralized Collagen Coatings By Aid Of Chitosan Nanospheres And Its Biological Evaluations

Besides good biological response capability, the coating on metal implant should have good capability on loading/releasing antibacterial drags or biological factors, so as to form a proper environment and accelerate the osseointegration process. Limited by the thickness and the porous morphology of the bioactive coating on metal implant, it is not proper to load/release antibacterial drugs or biological factors. In this study, based on the research founding that the good cytocompatiblity and porous structure of mineralized collagen coating, we adopted a way of incorporating chitosan nanospheres into mineralized collagen coating to create a good capability of loading/releasing antibacterial drugs and biological factors, and the antibacterial effect and osseointegration effect of chitosan nanospheres incorporated coatings were evaluated. The main results were summarized as follows:The enhanced loading/release ability of antibacterial drugs by aid of chitosan nanospheres:Through the electrochemical deposition process, the chitosan nanospheres could be codeposited with mineralized collagen onto titanium plate, the chitosan nanospheres adhered tightly to the collagen fibrils. Due to the affinity between chitosan nanospheres and antibacterial vancomycin hydrochloride (VH), the release amount after1h was decreased from65%to37.2%, and the burst release of VH was depressed significantly. After96h, the release of VH could be still observed, demonstrating a sustained behavior. The antibacterial results showed that the VH loaded mineralized collagen-chitosan nanospheres coatings had a good antibacterial effect in both short and long period.The enhanced loading/release ability of growth factor (rhBMP-2) by aid of chitosan nanospheres:Through electrophoresis injection, the rhBMP-2loaded chitosan nanospheres could be injected into the porous structure of mineralized collagen coating, and the chitosan nanospheres adhered on the walls of porous coating. The loading amount of growth factor (rhBMP-2) was increased by1.7times, from446ng/cm2to1186ng/cm2. The release results showed that the effective release period was prolonged to more than30days. The in vitro results showed that the enhanced loading amount of rhBMP-2really accelerated the differentition and mineralization level of preosteoblasts. The in vivo tests showed that the pull-out strenghth of the implant covered by a coating with the enhanced loading amount of rhBMP-2was promoted by30.16%and its osseointegration could be basically completed only after implantation for8weeks.The incorporation of chitosan nanospheres into mineralized collagen coatings is a good way to significantly improve loading/release ability without impairing the high biological response capability, and finally antibacterial and osseointegration effects for the mineralized collagen coatings can be greatly improved.