ATernary Conjugated Polymer for NIR-II Fluorescence Imaging and Photothermal/Photodynamic Combination Therapy

In order to simultaneously achieve photothermal properties, photodynamic effects and second near-infrared (NIR-II 1000-1700 nm) fluorescence emission of conjugated polymers, herein a novel ternary conjugated polymer (BDP) was designed and synthesized by copolymerization of an electron-withdrawing monomer diketopyrrolopyrrole and two electron-donating monomers (benzodithiophene derivatives and 1,10-phenanthroline). Then water-soluble nanoparticles (BDP NPs) were further prepared by self-assembling with amphiphilic Pluronic F127 through nanoprecipitation method. The nanoparticles with a diameter of around 90 nm exhibited excellent stability in aqueous solution. The absorption and emission peaks of BDP NPs were determined to be 735 nm and 1039 nm, respectively. The mass extinction coefficient of the nanoparticles was as high as 4.67 mL/(mg center dot cm) the fluorescence quantum yield of BDP NPs was measured to be 0.62% by using IR-26 as a reference, and the photothermal conversion efficiency was 18.2%. Under 730 nm laser irradiation, the temperature of BDP NPs (150 mu g/mL) can reach 64 degrees C, which was high enough for photothermal therapy. Besides, the BDP NPs also produce reactive oxygen species with the same laser, which can be used for photodynamic therapy. Cell experiments confirmed that there was no obvious dark toxicity to both NIH3T3 cells and HeLa cells. While under NIR laser irradiation, strong phototoxicity toward cancer cells was observed, indicating the high therapeutic efficacy with the combination therapy. After intravenous injection of BDP NPs, the blood vessels in living mice can be observed which confirmed the high resolution of NIR-II imaging. Importantly, the BDP NPs can accumulate at the tumor sites at 12 h post-injection, indicating the possibility of NIR-II imaging guided combination therapy in vivo. Overall the obtained BDP NPs with high biocompatibility strong absorption in the first near-infrared (NIR-I, 650- 900 nm) range, intense emission in NIR-II region, and the ability to produce reactive oxygen species and hyperthermia were, excellent candidate for tumor diagnosis and phototherapy. In addition, this work also provides a promising method for the rational design of conjugated polymer-based high performance phototheranostic nanoplatforms. [GRAPHICS] .