Single-component organic semiconducting polymer nanoparticles for near-infrared afterglow imaging

Afterglow imaging holds great promise in the field of bioimaging owing to its ultrahigh imaging sensitivity. However, most reported afterglow imaging nanoprobes are prepared via nanoprecipitation, which both their stability and Förster resonance energy transfer (FRET) efficiency can further be improved. Herein, we report a single-component organic afterglow nanoprobe (PPVP-PEG) for lymph nodes and tumor imaging. PPVP-PEG is synthesized by conjugating both near-infrared (NIR) emitting photosensitizer (tetraphenylporphyrin, TPP) and poly(ethylene glycol) (PEG) onto side chains of polyphenylenevinylene (PPV). Such structure makes PPVP-PEG an amphiphilic copolymer that can self-assemble into water without the addition of stabilizer. PPVP-PEG has NIR afterglow emission and higher afterglow intensity than PPV-PEG without TPP conjugation. In addition, PPVP-PEG has a higher FRET efficiency between TPP and PPV than similar nanoprobe prepared via nanoprecipitation. The afterglow signal of PPVP-PEG can clearly detect lymph nodes of mice with high sensitivity. In addition, owing to the unique structure, PPVP-PEG shows excellent tumor targeting capability. Combining with the high sensitivity of afterglow imaging, the tumor can be imaged with high signal-to-background ratio. Thus, this work provides an approach to improve the stability and FRET efficiency of afterglow probe and may boost the development of afterglow imaging.