Self‐Assembled Semiconducting Polymer Nanoparticles for Ultrasensitive Near‐Infrared Afterglow Imaging of Metastatic Tumors

Detection of metastatic tumor tissues is crucial for cancer therapy; however, fluorescence agents that allow to do share the disadvantage of low signal‐to‐background ratio due to tissue autofluorescence. The development of amphiphilic poly(p‐phenylenevinylene) derivatives that can self‐assemble into the nanoagent (SPPVN) in biological solutions and emit near‐infrared afterglow luminescence after cessation of light irradiation for ultrasensitive imaging of metastatic tumors in living mice is herein reported. As compared with the counterpart nanoparticle (PPVP) prepared from the hydrophobic PPV derivate, SPPVN has smaller size, higher energy transfer efficiency, and brighter afterglow luminescence. Moreover, due to the higher PEG density of SPPVN relative to PPVP poly(ethylene glycol), SPPVN has a better accumulation in tumor. Such a high sensitivity and ideal biodistribution allow SPPVN to rapidly detect xenograft tumors with the size as small as 1 mm³ and tiny peritoneal metastatic tumors that are almost invisible to naked eye, which is not possible for PPVP. Moreover, the oxygen‐sensitive afterglow makes SPPVN potentially useful for in vivo imaging of oxygen levels. By virtue of enzymatic biodegradability and ideal in vivo clearance, these organic agents can serve as a platform for the construction of advanced afterglow imaging tools.