Optical agents with long-lasting light after cessation of excitation have great promise for ultrasensitive in vivo imaging due to eliminated tissue autofluorescence. However, such imaging agents are rare and generally limited to inorganic nanoparticles with relatively low brightness and short near-infrared (NIR) emission. In this study, we introduce a new generation of purely organic agents based on semiconducting polymer nanoparticles (SPNs) that can store photon energy via chemical defects and then emit long NIR afterglow luminescence at 780 nm after light irradiation. The in vivo afterglow of SPNs is more than two orders of magnitude brighter than that of concentration-matched inorganic agents, and the signal is detectable through an entire live mouse—a feat that is nearly impossible with NIR fluorescence imaging. Such a high sensitivity couple with the ideal biodistribution allow SPNs 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. Moreover, the structural versatility of SPNs enables a smart activatable afterglow probe with signal specific to the presence of biothiols permitting excitation-free real-time imaging of drug-induced hepatotoxicity in living mice. This study provides the basis for an entirely new class of optical reporters for molecular imaging at a sensitivity level not achievable with conventional NIR fluorescence imaging.

Molecular afterglow imaging of semiconducting polymer nanoparticles

256th National Meeting (2018)

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