Naphthalimide‐Based Type‐I Nano‐Photosensitizers for Enhanced Antitumor Photodynamic Therapy: H 2 S Synergistically Regulates PeT and Self‐Assembly

Abstract Photodynamic therapy (PDT) relies on a combination of light and photosensitizers (PSs) to achieve local control over cancerous lesions. However, it is subject to limitations, including tumor hypoxia, low tumor targeting, off‐target phototoxicity, and always‐on fluorescence. Here, we propose a design strategy for activated nano‐PSs (N‐PSs) to simultaneously overcome the limitations of PDT, wherein photoinduced electron transfer (PeT) is coupled with an endogenous H 2 S‐regulated self‐association process to promote Type‐I photochemical reactions. Using theoretical calculations, spectral analysis, and microscopic imaging, we verified the generation of self‐assembly and occurrence of PeT. And it was also shown that H 2 S could synergistically inhibit the PeT and self‐assembly, reflecting by a 21‐fold increase in fluorescence intensity at 635 nm and 35‐fold enhancement of the Type‐I photochemical reaction as inferred from O 2 − generation. Moreover, the most promising self‐assembled N‐PS, Ts3‐ONB , was found to almost completely inhibit tumor growth in mice under two‐photon excitation through the synergistic regulation of PeT and self‐assembly by endogenous H 2 S ( V 14 days Ts3‐ONB + Light group / V 14 days Control group ≈ 0.02). As such, the synergistic combination of PeT and self‐assembly is an effective design strategy for developing advanced N‐PSs that can address some current PDT limitations.