Study On The Construction Of Photothermal Antibacterial Coating Enhanced By Metal Ion Release On The Surface Of Titanium-based Implants

Due to their excellent mechanical properties,good chemical stability and biocompatibility,titanium-based materials have been widely used in the preparation of orthopedic implants.However,titanium-based materials are not inherently antibacterial,and the bacterial infections that occur during utilization can lead to healthy problems to patients.In addition,the titanium-based material is biologically inert and has difficulty forming an effective integration with the surrounding bone tissue,which may lead to aseptic loosening of the implants.Concerning on the issues mentioned above,the construction of a multifunctional composite coating on the surface of titanium-based implants with excellent antibacterial properties and good osteoconductive functions through surface modification techniques can effectively improve their long-term stability in service in living organisms and has great scientific value.In recent years,photothermal antibacterial strategies have become attractive due to their advantages of being non-resistant,non-invasive and remotely controllable.However,continuously high temperature on the surface possibly bring damage on healthy tissue,while lower temperature cannot significantly inhibit bacteria.Alternatively,the release of active metal ions e.g.Zn²⁺,Fe³⁺,etc.also show an excellent antibacterial performance.Most of they are essential components of the enzymatic reaction of the organism,thus they can promote the regeneration of bone tissue as well It was reported that an appropriate increase of temperature（below 55℃）benefits in increasing permeability of bacterial cell membranes,and subsequently enhances the penetration of metal ions into bacterial cell,achieving a synergistic enhancement of antibacterial performance.The combination utilization of active metal ion release and photothermal therapy would show an excellent antibacterial property with high safety for human body,enhance osteoconstruction,prevent implant-related infections without damaging.In this study,a composite coating on the surface of pure titanium（Ti）with good antibacterial property and osseointegration ability were fabricated through the surface modification strategies of hydrothermal method,annealing treatment and nanomaterial immobilization.The main conclusions of this thesis are summarized as follows:（1）Construction and study of HT/ZIF-8@RIS coating with good photothermally antibacterial property and osseointegration ability:a spongy porous micro-nano multilayered structure was constructed by hydrothermal reaction with alkali,followed by the loading of a zinc-containing organometallic skeleton（ZIF-8）encapsulated with sodium risedronate（RIS）on the micro-nano structure by a secondary hydrothermal reaction,resulting in an organometallic skeleton drug-loaded micro-nano multilayered HT/ZIF-8@RIS composite coating with good photothermally antibacterial property and osseointegration ability.The experimental results show that the hydrothermally formed micro-nano multilayered structure enhances the absorption of near infrared light and endows the HT/ZIF-8@RIS coating a stable photothermal conversion capability.After 10 min of NIR（808 nm,0.6 W/cm²）irradiation,the surface temperature of the coating could be increased from 22℃ to 49.6℃ in in vitro,while the surface temperature can be increased from 36.8℃ to 50.8℃ in in vivo,which is a safe temperature for human.The NIR irradiation enhances releasing zinc ions from the HT/ZIF-8@RIS coating,leading to an enhancement of antibacterial property in vitro and in vivo.The in vitro antibacterial efficiency against Escherichia coli and Staphylococcus aureus are 94.5%and 94.9%,respectively,while the in vivo antibacterial efficiency against Staphylococcus aureus achieves 96%.Moreover,the HT/ZIF-8@RIS coating shows good biocompatibility,pro-osteoblast proliferation and differentiation in vitro,as the cell viability of HT/ZIF-8@RIS group reaches 118%of that of the HT-Z group for 5 days’culturing,the collagen secretion of HT/ZIF-8@RIS group reaches 155%of that of the Ti group for 14 days’culturing,and extracellular matrix mineralisation of HT/ZIF-8@RIS group reaches 224%of that of the Ti group for 14 days’culturing.Furthermore,as-fabricated coating also show good biocompatibility in vivo.（2）Construction and study of FeOOH-Fe₂O₃ coating with good photothermally antibacterial property and osseointegration ability:a spongy porous micro-nano multilayered structure was constructed by hydrothermal reaction with alkali,followed by a secondary hydrothermal reaction with ferric chloride solution on the micro-nano structure,finally by annealing at different temperatures,resulting in an micro-nano multilayered FeOOH-Fe₂O₃ composite coating with good photothermally antibacterial property and osseointegration ability.The experimental results show that the FeOOH-Fe₂O₃ coating prepared by annealing at 450℃（F450）enhances the absorption of near infrared light and endows the F450 coating a stable photothermal conversion capability.After 10 min of NIR（808 nm,0.5 W/cm²）irradiation,the surface temperature of the coating could be increased from 22℃ to 50.4℃ in in vitro,while the surface temperature can be increased from 36.9℃ to 51.2℃ in in vivo,which is a safe temperature for human.The NIR irradiation enhances releasing iron ions from the F450 coating,leading to an enhancement of antibacterial property in vitro and in vivo.The in vitro antibacterial efficiency against Escherichia coli and Staphylococcus aureus are 98.3%and 96.5%,respectively,while the in vivo antibacterial efficiency against Staphylococcus aureus achieves 97.2%.Moreover,the F450 coating shows good biocompatibility,pro-osteoblast proliferation and differentiation in vitro,as the cell viability of F450 group still over 100%for 5 days’culturing,the collagen secretion of F450 group reaches 123%of that of the Ti group for 14 days’culturing,and extracellular matrix mineralisation of F450 group reaches 203%of that of the Ti group for 14 days’culturing.Furthermore,as-fabricated coating also show good biocompatibility in vivo.