Near-Infrared Triggered Rechargeable Singlet Oxygen Battery for Sustained Phototherapy: Fast Charging and Long-Lasting Discharging.

Photodynamic therapy (PDT) for deep-seated tumors is fundamentally constrained by limited tissue penetration, the ultrashort lifetime of singlet oxygen (1O2), and the lack of reusable oxygen delivery systems. Herein, we report a near-infrared (NIR) triggered rechargeable "singlet oxygen battery" that enables sustained and cyclic 1O2 supply for enhanced phototherapy. A series of aza-boron-dipyrromethene (aza-BODIPY) probes (NBDP, ABDP, and PBDP) are rationally engineered by integrating distinct 1O2 carriers, among which PBDP exhibits optimal performance. Upon 808 nm irradiation (5 min), PBDP nanoparticles (NPs), as the singlet oxygen battery, generate abundant 1O2 that is reversibly captured via [4+2] cycloaddition with 2-pyridone to form endoperoxides (EPOs), while simultaneously enabling efficient photothermal conversion. After light cessation, stored 1O2 is thermally released from EPOs for up to 1 h, realizing sustained therapeutic action. Notably, the system supports multiple charging-discharging cycles with negligible performance decay. In vivo NIR-II imaging reveals efficient tumor accumulation, leading to significant tumor suppression via synergistic sustained PDT/PTT (photothermal therapy) with excellent biocompatibility. This work provides a rechargeable 1O2 storage and release platform by integrating NIR activation, self-heating-assisted discharge, and cyclic phototherapeutic capability, offering a promising strategy to improve the efficiency and durability of phototherapy for tumor treatment.