Molecularly sculpted NIR-II nano-igniter converts local photothermal heat into systemic antitumor vaccination

Photothermal therapy (PTT) holds transformative potential for precision cancer treatment, yet clinical translation remains constrained by the scarcity of molecularly defined, biocompatible, and efficiently NIR-absorbing photothermal agents (PTAs). Here we report a rational donor-acceptor-donor (D-A-D) framework that delivers ultrasmall organic PTAs with record photothermal conversion efficiencies (49.8%) and intrinsic immunogenic cell death (ICD) activity. The design exploits 6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g]quinoxaline as a π-extended, multi-nitrogenated acceptor core flanked by trifluoromethyl groups to deepen the LUMO, while methoxylated triphenylamine donors intensify intramolecular charge-transfer and suppress radiative decay. Nanoprecipitation furnishes monodisperse nanoparticles that exhibit intense NIR-II absorption, exceptional photostability across five hyperthermic cycles, and lysosome-directed uptake. In vitro, single-dose FTPA NPs plus 808-nm laser irradiation trigger mitochondrial depolarization, G0/G1 arrest, and apoptosis in > 70% of 4T1 cells while releasing abundant ATP and surface calreticulin-canonical ICD signals. A prophylactic vaccination model corroborates these molecular cues: mice primed with FTPA-NP-treated tumor cells reject contralateral challenge, achieving > 90% long-term survival, expansion of cytotoxic CD8⁺ T cells (≈ 70% activation), and suppression of Tregs (≈ 3%). No systemic toxicity or off-target pathology is observed. This study establishes a chemically tunable, metal-free PTA platform that synergizes thermal ablation with systemic anti-tumor immunity, providing a versatile scaffold for next-generation precision immuno-photothermal medicine.