Efficient radical generator with NIR emission by donor modulation for mitochondria-targeted photodynamic therapy

Development of NIR type I photosensitizers (PSs) that can specifically target subcellular organelles remains a significant challenge in photodynamic therapy (PDT). In this work, two D-π-A PSs named TPE-IN and TPA-IN were constructed via the strategy of changing donors. In detail, replacing donor group tetraphenylethylene (TPE-IN) with triphenylamine (TPA-IN) could extend the emission wavelength of PSs into the NIR-I region. Meanwhile, the singlet-triplet energy gap (ΔE_ST = 0.53 eV) of PSs was also narrowed, which efficiently promoted the production of superoxide anion radical (O₂^-) and hydroxyl radical (OH), especially for TPA-IN. Further mechanistic studies demonstrated that the generation of OH mainly relied on the cascaded electron-transfer process mediated by the Haber-Weiss reaction (O₂^- → H₂O₂ → OH). More importantly, TPA-IN could specifically accumulate in mitochondria through electrostatic interactions (Pr = 0.81), which could decrease mitochondrial membrane potential, inducing cell late apoptosis (95.8 %) upon light exposure. This study established innovative theoretical and technological groundwork for designing high-efficiency, precision-targeted optical theranostic agents aimed at eliminating cancer cells.