Rational Design of BODIPY-Diketopyrrolopyrrole Conjugated Polymers for Photothermal Tumor Ablation.

Conjugated polymers (CPs) have drawn growing attention in cancer phototherapy and imaging due to their large extinction coefficients, robust photostability, and good biocompatibility. Herein, we propose a new type of photothermal therapy materials on the base of BODIPY-diketopyrrolopyrrole (DPP) CPs, where the number of methyl substitutes at the β and β' positions on BODIPYs are variable, allowing us to investigate the interplay between the structure of the monomers and the related properties of CPs. Combining the experimental data with theoretical calculation, we concluded that with the decrease of the number of methyl moieties on the β and β' positions of BODIPY, the polymerization degree and solubility of the obtained CPs were improved, and the polymeric spatial planarization and degrees of conjugation increased, inducing the bathochromic-shift of absorption, which resulted the absorption spectra getting closer to the near-infrared (NIR) region and more conducive to the application of the conjugated polymers in vivo. Afterwards, the CP nanoparticles were made, and their photothermal activity in cancer therapy was validated by a series of in vitro and in vivo experiments. In this paper, we provide a new way to manipulate properties of CPs with great potential in photothermal therapy through the structural engineering.