Fabrication And Biological Properties Of Ni-Ti-O Nanopore Coating Incorporated With Cu On NiTi Alloy Surface

Nearly equiatomic nickel-titanium(NiTi)alloy has been widely used in orthopedic field because of its unique shape memory effect,super elasticity,low elasticity modulus and good biocompatibility.However,due to its poor antibacterial ability and biological activity,it is prone to infection after implantation,eventually leading to the failure of the implant.Proper nanoscale surface morphology can effectively improve the biocompatibility of materials.In addition,the loading of bioactive elements can also exert its biological effects.Therefore,combining the two different ways may hopefully solve the problem of NiTi alloy as implant.The present work incorporated biofunctional element copper(Cu)into Ni-Ti-O nanopores(NP-Cu)anodically grown on the surface of NiTi alloy through electrodeposition,and their antibacterial activity,cytocompatibility,and effects on the bone marrow mesenchymal stem cells(BMSCs),endothelial cells(ECs)and osteoblasts were investigated systematically.Based on the work,the research results obtained are as follows:(1)Ni-Ti-O NPs were firstly fabricated on the NiTi alloy by anodization,followed by incorporation of Cu into the NPs by electrodeposition.Incorporation of Cu(0.78-2.37 at.%)has little influence on the NP diameter,length,and morphology,and the Cu is uniformly distributed in the coating.(2)The NP-Cu coating can release Cu and Ni ions safely and effectively.In addition,the release level of Cu ions is in line with loadage,and the NP-Cu shows better antibacterial activity against gram-positive staphylococcus aureus(S.aureus)due to the release of Cu ions.The antibacterial rate increases from 60% for NP to 93% for NP-8Cu.(3)The NP-Cu coating shows better cytocompatibility.It can not only promote proliferation of BMSCs,but also stimulates type I collagen secretion and promotes extracellular matrix mineralization when compared with NP(control group).(4)The ionic extracts of NP-Cu has no significant effect on the proliferation and function of osteoblasts when compared with NP(control group).(5)The NP-Cu coatings have no influence on adhesion and activity of ECs,but can promote their proliferation.Lowest content of NP-Cu can significant promote the secretion of vascular endothelial growth factor(VEGF)of ECs.In addition,all the samples have no significant effect on nitric oxide(NO)synthesis.Therefore,better antibacterial ability and cytocompatibility of the NP-Cus render them to be promising when serving as NiTi implant coatings.