Fabrication And Light-responsive Antibacterial Coatings On Titanium Dental Implants

Titanium has been widely used as reconstructive and prosthetic material in orthopedics and dentistry due to its excellent mechanical properties,corrosion resistance and biocompatibility.However,postoperative infection is still one of the main reasons for the failure of titanium implants.Although a large number of studies have been carried out to endow the modified implants with anti-infection ability in situ by introducing organic,inorganic and other antibacterial agents on the surface of titanium,they can not be used in clinical practice due to the poor stability and toxicity.Systemic antibiotic therapy is still the standard of choice for the treatment of post implant infection,while the long-term and overuse of antibiotics have result in various problems,especially the emergence of drug-resistant bacteria.Recently,light-assisted antibacterial therapies have attracted much attention owing to the high antibacterial efficiency,no drug resistance,remote control and good biological safety.So they are considered to be effective therapies to solve the bacterial infections.In this dissertation,bioactive coatings were prepared on titanium by surface treatment technologies such as micro arc oxidation or/and hydrothermal treatment to impart the implants photo-responsive activity.The synergistic effect of photothermal therapy,photocatalysis and physical puncture by nanostructure make the modified implants possess in situ high efficiency anti-infection function.The main results are as follows:（1）Porous bioactive Ti O₂coating was firstly prepared by microarc oxidation on titanium,then graphene oxide（GO）was immobilized on the surface of Ti O₂coating by the introduction of polydopamine（PDA）with photothermal property.The results indicated that the GO-modified Ti O₂coating exhibited good photothermal and photocatalytic properties.The synergistic effects impart the coating to excellent antibacterial activity both in vitro and in vivo against Streptococcus mutans（S.mutans）under 808 nm near-infrared light irradiation within 20 min.Animal experiments also showed that the phototherapeutic system is safe biologically.（2）Molybdenum diselenide（Mo Se₂）was synthesized hydrothermally on the surface of porous Ti O₂coating prepared by micro-arc oxidation on titanium.To further improve the biocompatibility,chitosan was adsorbed on the surface of Mo Se₂nanosheets by electrostatic bonding.The results showed that the introduction of Mo Se₂significantly improved the photothermal and photodynamic ability of Ti O₂coating and made the implant possess excellent in vitro and in vivo antibacterial property against S.mutans under the irradiation of 808 nm NIR light for 15 min because of the synergistic of hyperthermia and reactive oxygen species（ROS）.The immobilization of chitosan improved the hydrophilicity and biocompatibility of Mo Se₂,and the hybrid coating promoted osseointegration even in the presence of infection in vivo under 808 nm light irradiation.（3）Ti O₂nanorod array was prepared on titanium by the hydrothermal treatment and the following pickling and annealing,then the donor of nitric oxide（NO）was grafted on the surface of nonorod by silanization.The results indicated that the light trap effect of nanostructure made the implant possess excellent and stable photothermal conversion property under the irradiation of 1060 nm near-infraredⅡlight,and the photothermal performance was gradually enhanced with the increase of laser power.After grafted with NO donor,the concentration of NO released from the nanorod array was gradually enhanced with the increase of temperature.Under the irradiation of near-infraredⅡlight,the combined actions of photothermal therapy,physical puncture by nanorod and NO eliminate S.aureus biofilms effectively in vitro and in vivo on titanium.The released NO also promoted the proliferation of endothelial cell and expression of VEGF,and the nanorod structure could promote the proliferation of mesenchymal stem cell and the improvement of related functions.The hybrid nanorod array could prevent bacterial infections and promote the new bone formation under 1060nm light irradiation,thereby enhancing osseointegration.