Hierarchically Hybrid Coatings On Ti Implants For Enhanced Antibacterial Activity And Osteogenesis

Objective:Titanium(Ti)implants are the preferred material for medical implants due to their excellent mechanical properties and biocompatibility.However,in clinical applications such as orthodontics and oral implantology,the dense oxide layer on the surface of Ti makes the material appear biological inert,resulting in slow osseointegration after implantation;and the surface of the material lacks antibacterial properties,resulting in treatment failures such as loosening and dislodging of implants due to bacterial infections.Therefore,the enhancement of the osseointegration capacity and the antibacterial properties of the Ti-based material are of great clinical value for implant applications.In this study,the pure Ti metal surface was modified by using a hierarchical composite coating.We systematically evaluated this composite coating modified Ti as a potential implant biomaterial with antimicrobial properties and osteogenic induction ability.Method:A uniform porous reticular nanostructure was fabricated via a simple alkali heat treatment(AHT).Subsequently,polydopamine(PDA)modification(PTi)was generated on the AHT surface by oxidative self-polymerization of dopamine in a weak alkaline environment.The catechol-rich structure of PDA with high adhesion property was utilized to facilitate the immobilization of nZnO.Finally,a chitosan(CS)/nanohydroxyapatite(nHA)blend coating was prepared by solvent casting to obtain a composite coating with a hierarchical structure and bioactive Ti surface(CS/nHA-nZnO-PTi).Physico-chemical properties were characterized by field emission scanning electron microscopy(FE-SEM),energy dispersive X-ray spectroscopy(EDS),Fourier infrared spectroscopy(FTIR),as well as water contact angle and protein adsorption experiments to assess the differences between the physicochemical properties of the samples at each step of the Ti surface composite coating construction.In addition,in vitro antibacterial activity of S.aureus and E.coli,cellular assays such as actin fluorescence staining,CCK-8 assay and alkaline phosphatase(ALP)activity were used to assess the differences in antibacterial properties,biocompatibility and osteogenic activity of the composite bio-coated Ti as well as between the different groups of the assay.Results:FE-SEM results showed significant differences in the surface appearance of the modified Ti in each group.The EDS showed that the Ca/P ratio of the CS/nHA-nZnO-PTi sample is approximately 1.71,which is very close to the theoretical value of 1.67 for hydroxyapatite.FTIR showed characteristic peaks of amide groups and phosphate functional groups in CS and nHA,all of which indirectly proved the successful expression of the CS/nHA coating.In vitro antibacterial activity experiments showed that the experimental group containing nZnO exhibited significant bactericidal properties compared with other groups,with the nZnO-PTi group showing the strongest bactericidal ability,with inhibition rates of 91.06% and 88.12%against Escherichia coli and Staphylococcus aureus,respectively.In vitro cell experiments showed that the nZnO-PTi group exhibited greater cytotoxicity,while the CS/nHA hybrid coating on the nZnO-PTi surface significantly promoted cell adhesion and proliferation,resulting in improved cytocompatibility in the CS/nHA-nZnO-PTi group compared to the nZnO-PTi group.This suggests that the CS/nHA coating can modulate nZnO to reduce cytotoxicity.Furthermore,the CS/nHA-doped coating on the nZnO-modified Ti surface significantly enhanced the osteogenic differentiation of MC3T3-E1 cells by up-regulating the protein expression of alkaline phosphatase(ALP),demonstrating superior osteogenic properties.In summary,the CS/nHA-nZnO-PTi composite coating of modified Ti has good antibacterial properties along with some osteogenic differentiation-promoting activity.Conclusion:1.Hierarchically hybrid CS/nHA-nZnO-PDA coating on Ti implants is successfully developed by oxidative self-polymerization,nanoparticle deposition,and solvent casting film formation,with the desired physicochemical properties required for biological implant materials.2.The CS/nHA-nZnO-PTi surfaces exhibit strong broad-spectrum antibacterial ability.3.The designed CS/nHA-nZnO-PTi surfaces improve cytocompatibility and the osteogenic differentiation of cells.