Preparation And In Situ Anti-biofilm Performance Of NIR Light Responsive Composite Coating On Titanium Implants

Prosthetic loosening and implant-associated infections of titanium(Ti)implants are main factors leading tothe failure of implantation.Micro-arc oxidation is considered tobe an effective and convenient strategy toconstruct bioactive TiO₂ coating with outstanding mechanical strength and osteogenic ability on the surface of Ti or its alloys.Simultaneously,antibacterial metal ions(such as Ag⁺,Cu²⁺and Zn²⁺)can be incorporated intothe TiO₂ coating during the oxidation process tomake the implants possess antibacterial activity.However,the toxicity of metal ions limits the clinical application of TiO₂ coating.Compared with the sterilization by metal ions,light-triggered antibacterial therapies have attracted more attention due toits remote control,precise treatment and higher antibacterial efficiency.Although TiO₂is an excellent photocatalyst,it can not be triggered by near-infrared(NIR)light due tothe wide band gap of 3.2 e V.Herein,a NIR light responsive composite coating was prepared on Ti implant toimpart excellent antibacterial ability under 808 nm NIR light.The specific research content is as follows:(1)Preparation and characterization of the composite coatingFirstly,MoS₂ modified TiO₂ coating was fabricated on Ti by a hybrid process of micro-arc oxidation and hydrothermal treatment toimprove the photothermal conversion and photocatalytic performance under 808 nm light irradiation.Subsequently,the surface of the MoS₂ was modified with polydopamine(PDA),which could further improve the photothermal ability of the hybrid coatings.Collagen,the main organic component of bone extracellular matrix,was immobilized on the surface of implant toimprove the biocompatibility.The analysis results of scanning electron microscope(SEM),X-ray photoelectron spectroscopy(XPS),and Fourier infrared spectroscopy(FTIR)show that the TiO₂ coating has a smooth surface with many pores of less than 5?m in pore size.After the hydrothermal treatment,MoS₂ nanosheets are evenly distributed over the surface of the microporous TiO₂coatings.Collagen was grafted on the surface of MoS₂-TiO₂(M-TiO₂)by Michael addition reaction or Schiff base reaction with dopamine.After modified with PDA,the structure of MoS₂changes from nanosheet tonanosphere,and the immobilization of collagen makes the nanospheres more closely arranged.In addition,the contact angle test results show that the Col/PDA/MoS₂-TiO₂(CPM-TiO₂)coating has good surface hydrophilic properties.(2)In vitroanti-biofilm performance of the composite coatingThe results of spread plate,fluorescent live/dead staining and SEM observation show that MoS₂-TiO₂(M-TiO₂),PDA/MoS₂-TiO₂(PM-TiO₂)and Col/PDA/MoS₂-TiO₂(CPM-TiO₂)can quickly remove Staphylococcus aureus(S.aureus)biofilm and Staphylococcus mutans(S.mutans)biofilm after 808 nm(0.8 W/cm²)illumination for 15 min.This is due tothe synergistic effect of reactive oxygen species(ROS)and heat generated by the MoS₂-TiO₂ composite material under near-infrared light irradiation,and the grafting of PDA and type I collagen has negligible effect on the antibacterial properties.(3)Biocompatibility and osteogenic properties of the composite coatingsThe results of fluorescence staining,SEM observation and MTT experiment show that the CPM-TiO₂ composite coating had good biocompatibility and could significantly promote the adhesion,spreading and proliferation of osteoblasts.In addition,the effects of local high temperature and ROS generated under NIR light on cell growth and proliferation are temporary.Animal model experiments prove that CPM-TiO₂ could quickly and effectively remove S.aureus biofilm in the body,and could alsosignificantly promote new bone formation.Furthermore,phototherapeutic system is safe and non-toxic toorganisms.