A Dual‐Function Hemicyanine Material with Highly Efficient Photothermal and Photodynamic Effect Used for Tumor Therapy

Abstract Small molecular organic optical agents with synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT), hold credible promise for anti‐tumor therapy by overcoming individual drawbacks and enhancing photon utilization efficiency. However, developing effective dual‐function PTT‐PDT photosensitizers (PSs) for efficient synergistic phototherapy remains challenging. Here, a benz[c,d]indolium‐substituted hemicyanine named Rh‐BI, which possesses a high photothermal conversion efficiency of 41.67% by exhaustively suppressing fluorescence emission, is presented. Meanwhile, the rotating phenyl group at meso‐site induces charge recombination to enhance the molar extinction coefficient up to 13.58 × 10 4 M −1 cm −1 , thereby potentiating the photodynamic effect. Under 808 nm irradiation, Rh‐BI exhibits significant phototoxicity in several cancer cell types in vitro with IC 50 values as low as ≈0.5 µM. Moreover, treatment of 4T1 tumor‐bearing mice with Rh‐BI under laser irradiation successfully inhibits tumor growth. In a word, an effective strategy is developed to build PTT‐PDT dual‐functional optical materials based on hemicyanine backbone for tumor therapy by modulating conjugation system interaction to adjust the energy consumption pathway.