Design of donor-acceptor conjugated polymers based on diketopyrrolopyrrole for NIR-II multifunctional imaging.

Diketopyrrolopyrrole (DPP) is an excellent photosensitizer and photothermal agent with the advantages of good planarity, strong electron affinity, high electron mobility, easy purification, easy structural modification and high molar absorption coefficient. It is regarded as one of the ideal choices for the design and synthesis of efficient organic photovoltaic materials. Therefore, two kinds of donor-acceptor (D-A) conjugated polymers were designed and synthesized with DPP as the acceptor, and their optical properties and applications in the near-infrared region were studied. The quantum yield (QY) of PBDT-DPP is 0.46%, and the highest temperature reached within 10 minutes after irradiation with a 660 nm laser is 60 °C. Another polymer, EDOT-DPP, has a QY of 0.48%, and its semiconductor polymer nanoparticle aqueous solution can reach 60 °C within 12 minutes under laser irradiation, achieving photothermal treatment of nude mice tumors. Both polymer NPs have good biocompatibility and promising applications in bioimaging and photothermal therapy.

D-A-D organic fluorescent probes for NIR-II fluorescence imaging and efficient photothermal therapy of breast cancer.

Near-infrared second region (NIR-II) fluorescent probes are used in the diagnosis of early cancer due to their high tissue penetration. However, there are still few reports on organic small molecule fluorescent probes with NIR-II fluorescence imaging (NIR-II FI) combined with efficient photothermal therapy (PTT). In this study, planar cyclopentadithiophene (CPDT) was incorporated into the twisted structural skeleton (D-A-D), and the strong acceptor TTQ molecule (A) and the donor triphenylamine (D) were introduced to synthesize an organic small molecule (TCT) with enhanced NIR-II fluorescence emission performance. To improve the hydrophilicity of TCT molecules, we used the nanoprecipitation method to coat DSPE-mPEG2000 on the TCT molecules and obtained nanoparticles (TCT-NPs) with a strong absorption band, good water dispersibility, and NIR-II FI ability, which realized NIR-II FI-guided PTT for breast cancer tumors. Due to their effective near-infrared absorption, TCT-NPs exhibit high photothermal conversion efficiency (η = 40.1%) under 660 nm laser irradiation, making them a photothermal therapeutic agent with good performance. Therefore, TCT-NPs have the potential to diagnose, eliminate, and monitor the diffusion of cancer.