A “donor–acceptor” structured semiconductor polymer for near infrared fluorescence imaging guided photodynamic therapy

Near infrared (NIR) fluorescence imaging guided photodynamic therapy (PDT) is a technique which has been developed in many clinical trials due to its advantage of real-time optical monitoring, specific spatiotemporal selectivity, and minimal invasiveness. For this, photosensitizers with NIR fluorescence emission and high 1O2 generation quantum yield are highly desirable. Herein, we designed and synthesized a “donor–acceptor” (D-A) structured semiconductor polymer (SP), which was then wrapped with an amphiphilic compound (Pluronic ® F127) to prepare water-soluble nanoparticles (F-SP NPs). The obtained F-SP NPs exhibit good water solubility, excellent particle size stability, strong absorbance at deep red region, and strong NIR fluorescent emission characteristics. The maximal mass extinction coefficient and fluorescence quantum yield of these F-SPs were calculated to be 21.7 L/(g ⋅ cm) and 6.5%, respectively. Moreover, the 1O2 quantum yield of 89% for F-SP NPs has been achieved under 635 nm laser irradiation, which is higher than Methylene Blue, Ce6, and PpIX. The outstanding properties of these F-SP NPs originate from their unique D-A molecular characteristic. This work should help guide the design of novel semiconductor polymer for NIR fluorescent imaging guided PDT applications.