Advancing NIR-II Photothermal Antibacterial Capability of Polydopamine Nanoparticles through Iron-Doped Molybdenum Oxide Functionalization

Polydopamine (PDA) exhibits admirable photothermal properties and biocompatibility for biomedical applications; however, its near-infrared (NIR-II) absorption and antibacterial performance remain insufficient. Herein, we introduced Fe-doped molybdenum oxide (MoFeOx) functionalized PDA composites exhibiting robust NIR absorption, reactive oxygen species (ROS) generation, and glutathione (GSH) depletion, thereby achieving a synergistic photothermal therapy/chemodynamic antibacterial effect. Polyethylenimine (PEI) served as the interlayer to bind MoFeOx onto the surface of PDA through electrostatic interaction. Compared with pure PDA, the nanoparticles demonstrated a 145% improvement in photothermal efficiency in the NIR-II range (1064 nm) when incorporating only 2.2% MoFeOx. This was attributed to the generation of electron "donor" and "acceptor" within the material, resulting in a reduction in the energy band gap and enhanced electron migration, as characterized by ultraviolet photoelectron spectroscopy (UPS). The nanoparticles exhibited synergistic therapeutic effects on E. coli and S. aureus through photothermal/chemodynamic therapy. This work offers an alternative methodology for improving the photothermal performance of PDA and designing synergistic antibacterial materials.