Enhancing electron transfer of a semiconducting polymer for type I photodynamic and photothermal synergistic therapy

Tumor hypoxia is responsible for the reduced therapeutic efficacy of type II photodynamic therapy (PDT) because of the dependence of cellular oxygen during (1)O(2) generation. Type I PDT may be a better strategy to overcome the disadvantages of hypoxia for enhanced theranostics. Herein, a new semiconducting polymer PDPP was synthesized and encapsulated with hydrophilic PEG-PDPA to enhance the electron transfer for type I PDT. PDPP NPs show a high superoxide radical generation ability with DHR123 as a probe. In vitro MTT assay indicates PDPP NPs with considerably high phototoxicity on human cervical cancer cells (HeLa) with a low half-maximal inhibitory concentration (IC(50)) of 6.1 μg/ml. Furthermore, an in vivo study demonstrates that PDPP NPs can lead to complete tumor suppression with the help of laser, compared with the control and dark groups. The biosafety is confirmed by the H&E analysis of the normal tissues (the heart, liver, spleen, lungs, and kidney). The results provide a strategy to design nanosystems for type I PDT and PTT synergistic therapy.