Highly bright stable organic radicals encapsulated by amphiphilic polypeptide for efficient near-infrared phototheranostics

Stable organic radical molecules have received extensive attention due to their unique electronic structure and photophysical properties, and the highly fluorescent quantum efficiency has great appeal to bioimaging. However, still scarce reports on the application of them on the therapy of tumors, especially theranostics. Here, 3,6-dibromocarbazole modified tris (2,4,6-trichlorophenyl) methane radical (TB) has been synthesized with high NIR fluorescence quantum efficiency, and free radical nanoparticles (NPs) have been prepared using the precursor of the radical doping strategy. The free radical molecule TB and its precursor molecule HTB were mixed in proportion and encapsulated with an amphiphilic polypeptide (PEG-PAsp) to obtain the NPs. The 4% NPs can achieve a high fluorescence quantum efficiency (18.68%) in the NIR region. In addition, the NPs also have a good ability to produce reactive oxygen species (ROS) under either normoxia or hypoxia conditions, which makes it possible for photodynamic therapy (PDT). Interestingly, the NPs also show preferable photothermal ability (PCE = 42.39%) for photothermal therapy (PTT). Both in vitro and in vivo studies reveal that the as-prepared radical NPS show a NIR fluorescence imaging-guided synergistic PTT and type I/II PDT to tumors. It provides new strategies and new clues for the application of free radical molecules in the theranostics of tumors.