Construction And Biological Properties Of ZnO Composite Coating On Titanium

Although zinc oxide(ZnO)has excellent antibacterial properties,it can not be used directly as implantable medical devices since its cytotoxity to mammalian cells,which is unfavourable to to cell adhesion and growth.In view of this,a variety of surface engineering technologies were ultilized to construct ZnO composite coatings on titanium surface including iron(Fe)doped ZnO coating,ZnO@Zn S nanorod array and ZnO@C nanorod array to study the relationship between the physicochemical properties of ZnO composite coatings and their antibacterial activities and cytocompatibility.The main results are as follows:(1)ZnO coatings were prepared on titanium surface by sol-gel method,and then treated by Fe plasma immersion ion implantation(PIII).It was found that Fe doping could improve the stability of ZnO and inhibit the burst release of Zn ions.Meanwhile,Fe would activate Fenton reaction to maintain the excellent antibacterial property of the composite coatings.The antibacterial rate of Fe doped ZnO coatings to Staphylococcus aureus(S.aureus,10~7 CFU/m L,24 hours)was over 95%.Fe doping significantly improved the cytocompatibility of ZnO coatings with human gingival fibroblasts(HGFs).(2)Core-shell ZnO@Zn S array was constructed on titanium surface by two-step hydrothermal method,namley ZnO nanorod arrays were firstly grown on titanium surface by hydrothermal method and then sulfurized with thioacetamide.ZnO nanorods array still maintained the nanorod-array structure after sulfurization.Sulfur(S)formed Zn S shell on the surface of ZnO nanorods through anion exchange,which could inhibit Zn release.At the same S source concentration,sulfurization time was the critical factor in regulating the biological properties of ZnO@Zn S nanorod array.With the extension of sulfurization time,the release rate of Zn got slower,resulting in relatively worse antibacterial activity.The antibacterial rate of ZnO@Zn S nanorod arrays with sulfurization time less than or equal to 6 h against Escherichia coli(E.coli)and S.aureus(10~7 CFU/m L,24 hours)was nearly 100%.The biocompatibility of ZnO nanorod arrays were improved after sulfurization,and the degree of improvement was positively correlated with sulfurization time.The ZnO@Zn S nanorod array promoted the adhesion and migration of HGFs(compared to smooth titanium,the numbers of adhered and migrating HGFs on ZnO@Zn S nanorod array with 6 h sulfurization increased to 140%and 130%,respectively).However,the proliferation rate of HGFs on ZnO@Zn S nanorod array was still significantly lower than that on titanium.(3)ZnO nanorod arrays coated with polydopamine were fabricated on titanium surface by hydrothermal growth followed by reaction in dopamine solution,and annealed in argon atmosphere to prepare ZnO@C nanorod arrays coated with carbon shell.C-coated ZnO maintained the structure of nanorod-array.The antibacterial rate of ZnO@C against E.coli and S.aureus was close to 100%(10~7 CFU/m L,24 hours).The cytocompatibility of ZnO@C was excellent.HGFs could adhere,grow and proliferate normally on its surface compared to ZnO.The improved cytocompatibility of ZnO@C was likely stemed from the reduction of ROS generation of ZnO by argon annealing and the barrier of C shell preventing direct contact between ZnO surface and HGFs.