Photo‐Triggered Fluorescence Polyelectrolyte Nanoassemblies: Manipulate and Boost Singlet Oxygen in Photodynamic Therapy

Photodynamic therapy (PDT) is a clinically approved therapeutic modality that has shown great potential for cancer treatment. However, there exist two major problems hindering PDT applications: the nonspecific phototoxicity requiring patients to stay in dark post‐PDT, and the limited photodynamic efficiency. Herein, we report a photo‐triggered porphyrin polyelectrolyte nanoassembling (photo‐triggered PPN) strategy, in which porphyrin photosensitizer and photoswitchable energy accepter are assembled into polyelectrolyte micelles by a combined force of charge interaction and metal‐ligand coordination. The polyelectrolyte‐based PPN exhibits good biocompatibility, and bestows a unique "confining isolated" inner microenvironment for fully overcoming the π‐π stacking of porphyrins with significant photodynamic efficiency (123‐fold enhancement). Due to the high Förster resonance energy transfer (FRET) (91.5%) between porphyrin and photoswitch in closed‐form, we could use light as a specific trigger to modulate photoswitch between closed‐ and open‐form, and manipulate the 1O2 generation in three stages: pre‐PDT (quenching 1O2 generation), during PDT (activating 1O2 generation), and post‐PDT (silencing 1O2 generation). This de novo strategy has for the first time realized remotely manipulating and boosting 1O2 generation in PDT, well resolving the critical and general challenges of limited photodynamic efficiency and side effects from nonspecific phototoxicity.