A Fluorinated Conjugated Polymer Allows for Enhanced NIR-II Fluorescence Imaging-Guided Photothermal Therapy

Precision cancer diagnosis is instrumental in optimizing photothermal anti-tumor therapy protocols. Powerful motivations have been expressed to construct conjugated polymers with near-infrared fluorescence and phototherapeutic behavior. However, it is a dilemma to simultaneously materialize a favorable fluorescence quantum yield (QY) and impressive photothermal conversion efficiency (PCE) as determined by the contradictory photophysical processes. Herein, a typical donor-acceptor structural photothermal agent (PTA) is synthesized, with synergistic elevation of QY and PCE, featuring various donors attached to 2-(2-decyltetradecyl)-6,7-dimethyl-2H-[1,2,3]triazolo [4,5-g] quinoxaline acceptor. By virtue of the fluorination strategy to modulate intramolecular D-A interaction and intermolecular stacking states, as well as increasing the recombination energy and non-radiative transitions, as confirmed by solvatochromic effect, the grazing incident wide-angle X-ray diffraction test, and theoretical analyses, the fluorinated polymeric PTA presents superior near-infrared-II (NIR-II) QY of 2.73% and PCE of 67.3%, outperforming its non-fluorinated counterpart. Ultimately, PQTz-fTT is engineered for in vivo NIR-II fluorescence imaging of blood vessels with a high signal-to-noise ratio of 3.14, as well as NIR-II imaging-guided photothermal anti-tumor therapy, enabling 100% tumor ablation on the 4th day with no recurrence over 21days post-treatment. This work further deepens insight into leveraging fluorination strategy to design highly efficient NIR-II fluorophores for cancer diagnosis and therapy.