Semiconducting Photosensitizer-Incorporated Copolymers as Near-Infrared Afterglow Nanoagents for Tumor Imaging

The fact that cancer metastasis is the main cause of death for most cancer patients necessitates the development of imaging tools for sensitive detection of metastases. Although optical imaging has high temporospatial resolution, tissue autofluorescence compromises the sensitivity for in vivo imaging of cancer metastasis. Herein, the synthesis of a series of photosensitizer-incorporated poly(p-phenylenevinylene)-based semiconducting copolymers and their utility as near-infrared (NIR) afterglow imaging nanoagents that emit light after cessation of light irradiation are reported. As compared with nondoped nanoparticles, the nanoparticles derived from the photosensitizer-incorporated copolymers have red-shifted NIR luminescence and amplified afterglow signals, allowing the detection of tiny peritoneal metastatic tumors almost invisible to naked eye. Moreover, the intrinsic oxygen-sensitive nature of afterglow makes those nanoagents potentially useful for in vivo imaging of oxygen levels. Thus, this study introduces a generation of light-excitation-free background-minimized optical imaging agents for the sensitive detection of diseased tissues in vivo.