Surface decoration of black phosphorus nanosheets to generate oxygen and release 1 O 2 for photodynamic killing of bacteria

Photodynamic therapy (PDT) has evolved as an essential method for infection control, but is confronted with challenges in terms of low oxygen supply, possible toxicity during light irradiation, and nonpersistent action. Herein, to address these limitations, black phosphorus (BP) is used as a photosensitizer and decorated with Pt nanoparticles and aminobenzyl-2-pyridone (APy) moieties to obtain BP@APy-Pt. The stability of BP is improved through the capture and occupation of lone-pair electrons after reductive deposition of Pt nanoparticles and covalent conjugation of APy. Pt nanoparticles on BP@APy-Pt catalyze the decomposition of endogenous H O to produce oxygen for consecutive cycles with a stable production capacity. The light exposure to BP@APy-Pt generates significantly higher O levels than those of BP/light, and the generated O is partially captured by APy moieties. The captured O during 20 min of illumination shows a constant release for 24 h in the dark. The cycled storage and release feature eliminates the toxicity of O at high levels during illumination and leads to efficient destruction of S. aureus and P. aeruginosa. Compared to the healing rates after treatment with BP/light (57.6%), BP@Pt/light (64.8%), BP@APy/light (77.8%), and BP@APy-Pt (48.5%), the skin wounds with infected S. aureus are fully healed after BP@APy-Pt/light treatment. Blood vessels and hair follicles are regenerated to resemble those of normal skin. Thus, this study expands the PDT strategy through integration with oxygen generation, O storage, and persistent release to promote bactericidal efficacy and eliminate side effects.