Advances in photothermal therapy for antibacterial biomedical materials: Photothermal agents, near-infrared windows, and combination strategies

Bacterial infections, particularly those involving multidrug-resistant pathogens and biofilm-associated infections in wound and implant-related settings, remain difficult to treat with conventional antibiotics alone. Photothermal therapy (PTT) has emerged as a non-antibiotic antibacterial strategy owing to its localized heat generation, broad-spectrum antibacterial activity, spatial controllability, and low risk of inducing conventional drug resistance. The antibacterial efficacy of PTT is largely governed by photothermal agents (PTAs), whose light absorption capacity, photothermal conversion efficiency, structural stability, biosafety, and bacterial interfacial interactions determine therapeutic performance. This review summarizes recent advances in antibacterial PTT from the perspectives of PTA design, excitation windows, and therapeutic integration. Representative first near-infrared window (NIR-I) PTAs, including noble metal nanomaterials, carbon-based nanomaterials, metal sulfides/oxides, metal-organic frameworks, and organic PTAs, are discussed with emphasis on their structural characteristics, photothermal mechanisms, surface regulation strategies, and antibacterial performance. Recent progress in second near-infrared window (NIR-II) PTAs is then highlighted, particularly their advantages in deeper tissue penetration, biofilm treatment, imaging-guided therapy, and precise intervention in complex infections. PTT-based combination strategies involving photodynamic therapy, chemodynamic therapy, and immunotherapy are also reviewed to illustrate how localized heat can synergize with oxidative damage, catalytic radical generation, immune modulation, and infection microenvironment regulation to enhance antibacterial efficacy. Finally, challenges and future directions of antibacterial PTT are discussed, including improving PTA stability and biocompatibility, minimizing thermal damage to normal tissues, enhancing infection-site responsiveness, and promoting clinical translation. Overall, this review provides a materials and biointerface perspective on how PTA design, NIR excitation, and therapeutic integration can guide the development of effective antibacterial photothermal platforms and their clinical translation.