Study of influence of intensity and ionizing radiation type on some porphyrins with application in cancer therapy

This paper presents the experimental results obtained in a study concerning the effects of ionising radiation (electron and photon beam) of different intensities (200 - 30.000 R) and/or light on tetra-kis-p-sulfonato-phenyl-porphyrin (TSPP) in water solutions as a new and efficient sensitizer efficiently used in photodynamic therapy of cancer . The spectral changes upon ionising irradiation of TSPP show the formation of phlorins. When these irradiated porphyrins solutions were exposed to light, J - and H -aggregated species were generated. The small intensity of ionising radiation stimulate H-aggregation. Different proportions (experimentally determined) of singlet and triplet excited states are formed initially on ionising irradiation as compared with light irradiation of water-solutions of TSPP. In the case of firstly ionising irradiation, the subsequently light irradiation yields to the generation of triplet states, the proportions of initially ratio triplet: singlet excited states being normally around 3:1, whereas with sensitiser TSPP firstly excited with light and after that with ionising radiation, the singlet excited state of TSPP will be the major species but at a generation rate more reduced than using ionising radiation excitation. Another important difference between light and ionising irradiation the formation of excited states is independent of the light absorption of the solute and solvent. The singlet oxygen formation , so the photochemical efficiency in photodynamic therapy of cancer is enhanced if face-to-face configurations (H-aggregated forms) are formed. The porphyrin is efficiently incorporated in a monomeric form in granulocytes and leukocytes and in a J-aggregate fluorescent forms but only in granulocytes. (authors)