Conjugated Polymer Nanoparticles with Absorption beyond 1000 nm for NIR-II Fluorescence Imaging System Guided NIR-II Photothermal Therapy

The second near-infrared fluorescence imaging (NIR-II FI) guided NIR-II photothermal therapy (PTT) possesses advantages for cancer treatment because of its accurate diagnosis and enhanced therapeutic effects for cancer. However, developing a conjugated polymer with both excellent NIR-II fluorescence and NIR-II PTT properties encountered many hindrances, including strong nonradiative decay, low solubility in organic solution, and significant aggregation-caused quenching (ACQ) effect. Herein, a conjugated polymer TTQ-2TC with optimized absorption in NIR-II regions, good solubility in organic solvents, and bright NIR-II FI signals is obtained through introducing the alkyl-side-chain-modified bithiophene (2TC) as the electronrich donor unit. The water-soluble nanoparticle (TTQ-2TC NPs) prepared from the conjugated polymer TTQ-2TC is used for precise NIR-II FI guided NIR-II PTT treatment. The in vivo blood and tumor imaging and therapy results show that the TTQ-2TC NPs possess high signal-to-background ratio (SBR) and perfect antitumor efficacy by NIR-II PTT.