Fabrication of conjugated polymers with aggregation-induced near-infrared-II emission for efficient phototheranostics.

ABSTRACT

Conjugated polymers (CPs), which emit in the second near-infrared window (NIR-II, 1000-1700 nm), are used as biomaterials for NIR-II fluorescence imaging because of their adjustable photophysical properties and high optical stability. However, the fluorescence signal of conventional CPs is quenched in an aggregated state due to strong π-π stacking, which results in the closure of the radiation attenuation pathway. To solve this problem, the aggregation-induced emission effect is considered a reasonable strategy for enhancing the aggregative fluorescence of IR-II emitters. We herein report NIR-II conjugated polymers with typical AIE characteristics (αAIE > 3) by changing the side chain structure of receptor units and the conjugation degree of donors. Conjugated polymer nanoparticles (PoBVT NPs) exhibit outstanding performance in NIR-II fluorescence imaging (QY = 1.94%) and highly effective photothermal therapy (η = 45%). In vivo studies have shown that the location of tumors can be accurately obtained by NIR-II FL/NIR-II PA imaging, and there is a significant anti-tumor effect after laser irradiation. This work offers prospects for the design of multifunctional conjugated polymers for NIR-II FL/PA imaging to guide NIR-II PTT applications.