Construction and antibacterial performance study of strontium-doped TiO ₂ coatings with photothermal-chemical synergistic antimicrobial properties

The inert surface of titanium (Ti) leads to inadequate osseointegration and bacterial infection, which are critical factors contributing to the failure of Ti implants. Micro-arc oxidation (MAO) technology enables the formation of a biocompatible porous TiO₂coating on Ti surfaces, offering advantages such as a simple fabrication process, strong adhesion to the substrate, and the ability to incorporate functional ions (e.g. Ag⁺, Cu²⁺, Sr²⁺). This modification significantly enhances cellular adhesion and osteogenic activity. However, the TiO₂produced via MAO exhibits a wide bandgap (3.2 eV), responding primarily to ultraviolet light, which results in low photothermal conversion efficiency in the near-infrared (NIR) region with greater tissue penetration, thereby limiting its application in photothermal therapy (PTT). This study was based on Sr²⁺-doped TiO₂coating, and its NIR photothermal efficiency was improved through surface modification with a metal-polyphenol network (MPN). Additionally,<i>ϵ</i>-poly-L-lysine (EPL) antimicrobial peptides were grafted onto the surface to establish a synergistic photothermal-chemical antibacterial system. Experimental results demonstrated that the TiO₂-MPN-EPL composite coating exhibited high-efficiency photothermal conversion under 808 nm laser irradiation, with the synergistic action of EPL providing targeted membrane disruption of bacteria. This system achieved a high bactericidal rate against<i>Staphylococcus aureus</i>and<i>Escherichia coli</i>while mitigating the thermal damage risks associated with standalone PTT. Furthermore, it promoted the proliferation of MC3T3-E1 osteoblasts.