PEGylate engineering for preparing water-soluble deep/near-infrared red type I/II photosensitizer and its efficient photodynamic therapy of cancer cells

Photodynamic therapy has still received more research attention because of its significant advantages of minimally invasive, high selectivity and non-drug-resistance. Photosensitizer is one of important compositions in the photodynamic therapy process, which could be divided into two categories of containing energy transfer dominant process (type II) and electron transfer dominant process (type I) from triplet state to oxygen. Usually, type I photosensitizers have the merit of low oxygen dependence, leading them to become a popular and important candidate for treating cancers because there is hypoxic environment in the solid tumor. However, poor water solubility and short emissive wavelength of reported type I photosensitizer make them suffer certain limitation in clinical application. Hence, it is urgent to develop water-soluble near-infrared red type I photosensitizer. Herein, choosing classical biocompatible macromolecule of polyethylene glycol to modify the designed ionic type I photosensitizer with aggregation-induced near-infrared red fluorescence to prepare a new water-soluble polymeric type I/II photosensitizer (named as PEG-MTPABZ-PyC). PEG-MTPABZ-PyC displays remarkable water solubility (37 mu g/mL), and maximal fluorescent wavelength peaks at 670 nm and extends to 850 nm of tail of fluorescent spectrum in aqueous solution, which endows it better efficiency of labelling cells by the significant red fluorescence. Additionally, its superior type I/II reactive oxygen species provide better killing of cancer cells in vitro. This study provides an effective method to prepare water-soluble near-infrared red type I/ II photosensitizer, which exhibits satisfactory photophysical property and biocompatibility as well as excellent efficiency for killing cancer cells under normoxia and hypoxia, offering great potential for clinical disease treatment.