Organic nanoparticles based on aza-boron dipyrromethene derivatives for combined photothermal and photodynamic cancer therapy

Cancer is one of the major diseases that threaten human being's health and life. Recently, phototherapy has gained great attention due to the advantages of high selectivity and low toxicity. Nonetheless, the development a single photosensitizer capable of simultaneously achieving photothermal and photodynamic effects remains a great challenge. Aza-boron-dipyrromethene (aza-BODIPY) dyes have been widely studied in biomedical area for their significant absorption in the near infrared region and high fluorescence quantum yield. In this contribution, three aza-BODIPY molecules (TAS-BP, TES-BP and TESO-BP) that conjugated with triphenylamine (TPA) or tetraphenylethylene (TPE) were designed and synthesized. The presence of donor-acceptor-donor pairs within compounds enables the intermolecular electron transfer, leading to the augmentation of near-infrared (NIR) absorbance and the generation of non-radiative heat. The nanoparticles were prepared via the assembly of the related organic compounds with amphiphilic polymer (DSPE-PEG2000), which were named as TAS-BP NPs, TES-BP NPs and TESO-BP NPs, respectively. Importantly, three nanoparticles can generate heat and reactive oxygen species (ROS) simultaneously induced by a single laser (808 nm). The photothermal conversion efficiency of TAS-BP NPs, TES-BP NPs and TESO-BP NPs were determined to be 64.5%, 65.7%, and 53.6%, respectively. Furthermore, the cellular experiments demonstrated the good biocompatibility and outstanding photocytotoxicity of three nanoparticles, and the TES-BP NPs exhibited the highest photodynamic/photothermal synergistic effect. Thus, the as-prepared organic nanomaterials were demonstrated as potential candidates for cancer treatment through phototherapy.