Preparation,Characterization And Osteocompatibility Evaluation Of Strontium-Magnesium Co-Doped Calcium Phosphate Coating On Ti6Al4V

With the increasingly significant trend of global population aging,tooth defects caused by tooth loss and oral diseases have raised public attention on oral health.Dental implants have become the best choice for treatment after tooth loss because they can not only achieve excellent repair of masticatory function,but also meet people’s aesthetic requirements.Titanium and titanium alloys are considered as one of the most suitable implant materials owing to their excellent biocompatibility and corrosion resistance.Combined with the micro-and nano-morphology constructed by surface treatment technology,titanium based implants are thought to form mechanical locking with surrounding bone tissue.In view of the limited role of traditional physical and chemical methods in improving osteocompatibility,coating techniques as a secondary processing method are applied to improve osteoinductivity of implants,which has become an important surface modification strategy.Bioactive calcium phosphate coating,which is regarded to have similar chemical composition to natural bone apatite in human body,is conducive to doping inorganic ions so as to mimic the physiological role of specific trace elements in bone tissue.Among many preparation methods of calcium phosphate coating,plasma spraying is the only commercial technique.Nevertheless,the existence of coating defects including phase decomposition,poor adhesion strength,nonuniform coating and low coating density makes it difficult to fully meet the performance requirements for surface coating on implants.Therefore,we aimed to explore a more efficient and pratical alternative method to prepare bioactive calcium phosphate coating on titanium based implants.In this paper,sol-gel method and biomimetic method were applied to the acid etched and alkaline etched surface of titanium alloy（Ti6Al4V）respectively to prepare Sr-Mg co-doped calcium phosphate coating based on the proven effects of Sr²⁺and Mg²⁺on promoting osteogenesis and angiogenesis.The physicochemical and biological properties of the as-prepared coatings were characterized.The details are as follows.（1）In this paper,a micro-structured surface with suitable roughness and good hydrophilicity was constructed on Ti6Al4V substrate by acid etching.By controlling the concentration of sol-gel precursor solution and sintering temperature,hydroxyapatite（HA）coating with compact and uniform structure,high crystallinity and roughness was then prepared by sol-gel method.It was found that after incorporating Sr²⁺and Mg²⁺into HA coating with different proportion and amount,all groups showed no cytotoxicity and could support cell survival and normal growth,although proliferation was inhibited to some extent at the amount of 10 mol%Sr²⁺.The doped ions significantly enhanced the effects of HA coating on promoting osteogenesis and angiogenesis.At the amount of 5 mol%Sr²⁺and 10 mol%Mg²⁺,the effects were shown to be the most significant.（2）We also managed to construct an interconnected and porous nano-structured surface with super-hydrophicility on Ti6Al4V substrate via alkaline etching.The substrate was immersed in simulated body fluid added with 5 mol%Sr²⁺and 10 mol%Mg²⁺in biomimetic method and by controlling the mineralization time,uniform Sr-Mg co-doped bone-like apatite（BA）coating was thus prepared.Compared to HA coating with the same amount of doped ions prepared by sol-gel process,in spite of good cytocompatibility,BA coating prepared by biomimetic method showed less capability to promote osteogenesis and angiogenesis,given the less bioactive ion release.In summary,this study proved that both sol-gel method and biomimetic method could be utilized to prepare Sr-Mg co-doped calcium phosphate coating on titanium alloy substrate and thus enhance osteogenesis and angiogenesis.The most significant synergistic promoting effect was found at the amount of 5 mol%Sr²⁺and 10 mol%Mg²⁺,which was believed to provide guidance for implant modification and osseointegration improvement.