Perylene tetracarboxylic acid-folate conjugated carbon quantum dots for targeted photodynamic therapy of prostate cancer.

This study reports the facile one-pot hydrothermal synthesis of water-soluble perylenetetracarboxylic dianhydride (PTCDA) conjugated carbon quantum dots (Per CDs) and their folate conjugate (PerFACDs), addressing the insolubility of PTCDA, a promising photosensitizer. Both CDs were thoroughly characterized using HRTEM, FTIR, Raman, and XPS techniques. Their singlet oxygen quantum yield (Φ), zeta potential, absorption and photoluminescence spectra were also studied. Their anti-human prostate cancer activity was tested using PC-3 cells as a model. The mode of cell death was investigated using flow cytometry, and their heamolytic activity and effect on the viability of normal peripheral blood mononuclear cells and were evaluated to assess the safety. The produced CDs were uniform spheres with diameters below 8 nm. At physiological pH, PerCDs exhibited a surface charge of -9 mV, while PerFACDs had -12 mV and a Φ of 0.22. The biocompatibility and cytotoxicity of the produced CDs were evaluated in vitro normal human fibroblast (HFF-1) cells, and peripheral blood cells. Both PerCDs and PerFACD showed negligible toxicity toward normal cells. To assess selective cytotoxicity, the selectivity index (SI) was calculated under dark conditions, yielding values of 1.47 for PerCDs and 2.4 for PerFACD, indicating significantly enhanced selectivity of PerFACD toward PC3 cells. Upon illumination using monochromatic 520 nm light-emitting diode (1.5 mW/cm), a total eradication of PC-3 cells was achieved within 60 min of irradiation using Per FA CD that was significantly more potent than Per CDs. Per FA CDs-PDT induced an apoptotic cell death mode at shorter irradiation times and a necrotic one at longer durations. These findings suggest that our synthesized third generation photosensitizer Per CDs and Per FA CD hold promise as safe and effective candidates for targeted PDT of prostate cancer.