Promoted intramolecular photoinduced-electron transfer for multi-mode imaging-guided cancer photothermal therapy

To develop smart and efficient near-infrared (NIR) organic dyes for photothermal cancer therapy is of great challenge. Herein, a pH-sensitive NIR dye BTN with donor–acceptor–donor scaffold has been synthesized. Two periphery electron-donating dimethylamine groups in BTN can not only promote the intramolecular photoinduced electron transfer (PET), but also bind protons to transform into electron-deficient ammonium cation for enhanced intramolecular charge transfer (ICT) under acidic circumstance. Through enveloping with amphiphilic polymeric 1,2-distearoyl-ras-glycerol-3-phosphatidyl ethanolamine-N-polyethyleneglycol-2000 (DSPE-mPEG₂₀₀₀), BTN nanoparticles (NPs) were fabricated with robust NIR absorption covering 600–900 nm, excellent photothermal conversion efficiency (43.2%), and good photostability. Additionally, BTN NPs can selectively target lysosomes. Through tailing intravenous injection into tumor-bearing nude mice, BTN NPs demonstrate outstanding photoacoustic/photothermal/fluorescence imaging-guided photothermal therapy for tumor ablation. Graphic abstract: [Figure not available: see fulltext.].