SiO₂-Coated ZnO for Photothermal and Photodynamic Antibacterial Applications in Bone Repair

Poly(L-lactic acid) (PLLA) is a promising material for bone substitutes due to its biodegradability and biocompatibility. However, its limited osteogenic activity and antibacterial properties restrict its applications. To address these challenges, this study develops PLLA/SiO₂@ZnO/PDA/PLL composite fibrous materials using an approach that integrates electrospinning with ultrasonic techniques. The composite exhibits photothermal antibacterial functionality and osteoinductive properties. The material demonstrates excellent hydrophilicity, sustained-release capability, and antibacterial activity. Upon near-infrared light exposure, Zn²⁺ ions are released, disrupting bacterial membranes via electrostatic interactions and lipid peroxidation induced by reactive oxygen species. This dual mechanism leads to bacterial membrane rupture and biofilm degradation. Zn²⁺ ions also interfere with bacterial respiratory enzymes, disrupting the electron transfer process and achieving efficient antibacterial effects. The composite further shows outstanding biocompatibility and osteoinductivity, promoting vascular endothelial cell and osteoblast adhesion and enhancing calcium-phosphate salt deposition. In vivo studies confirm its safety with no significant toxicity or adverse effects on tissues and organs. This PLLA/SiO₂@ZnO/PDA/PLL composite offers significant potential for repairing infected bone tissue and provides a strong foundation for future applications in bone tissue engineering.