Extension of π-system of silylated porphyrin derivative for photodynamic therapy

A silyl-substituted tetrabenzoporphyrin derivative has been designed to improve the light absorption efficiency of the corresponding silyl-substituted porphyrin derivative via small chemical modifications. By extension of the pi-conjugated system of the porphyrin derivative, its UV-vis absorption band was red-shifted and its molar absorption coefficient was increased. Although the extension of the pi-conjugated system of the porphyrin derivative led to slight decreases in the quantum yield of singlet oxygen photosensitization and cellular uptake efficiency, the photodynamic activity against HeLa cells was increased 12-fold. The efficiency of the photosensitization of singlet oxygen in HeLa cells was estimated and the enhancement in photodynamic activity was mainly explained on the basis of the increase in light absorption efficiency. The effects of silylation on the photodynamic properties of tetrabenzoporphyrin derivatives have also been studied. Silylation increased cellular uptake efficiency for HeLa cells, although the UV-vis absorption properties and quantum yield of singlet oxygen photosensitization were almost independent of silylation. This increase in cellular uptake efficiency led to an improvement in photodynamic activity. By the combination of silylation and extension of the pi-conjugated system of a porphyrin derivative, an efficient photosensitizer has been developed. (C) 2017 Elsevier B.V. All rights reserved.