Photochemical Properties of Carboranyl-Substituted Zinc Phthalocyanine

The photochemical properties of the o-carboranyl derivative of zinc phthalocyanine (ZnCPPc) have been studied. Spectral and kinetic characteristics of the excited singlet (τfl = 3.0 ns, Φfl = 0.06, λmax = 685 nm) and triplet states (τT = 0.47 ms, λmax = 500 nm) of the dye have been determined. The quantum efficiency of singlet oxygen formation for ZnCPPc in 2-methyltetrahydrofuran (2MeTHF) has been found (ΦΔ = 0.50). The formation of noncovalent complexes of the dye with human serum albumin was established, and the binding constant was determined. Confocal microscopy demonstrated the accumulation of ZnCPPc in HCT116 colon adenocarcinoma tumor cells. Under photoexcitation with 650-nm light, photosensitizing activity of ZnCPPc was detected in the micromolar concentration range (IC50 = 10 ± 0.5 μmol/L) without death of HCT116 cells under similar conditions in the dark, confirming the potential of this compound as a photosensitizer for photodynamic therapy.