Influence of the substitution of 3-vinyl by 3-formyl group on the photodynamic properties of chlorin P6: Molecular, cellular and in vivo studies

Molecular in vitro and in vivo properties of 3-devinyl-3-formylchlorin p6 ( FCp6) were examined in order to characterize this derivative as a new prosp ective photosensitizer. The long-wavelength absorption maximum of FCp6 was 690-696 nm (depending on environment). FCp6 was found to bind readily to me mbranous structures and form complexes with some proteins. The dye was asso ciated with the plasmalemma and distributed rather diffusely along the cyto plasm with ca a three-fold higher accumulation within mitochondria in A549 human adenocarcinoma cells. The spectral analysis revealed that the major p art of FCp6 was bound to membranes within cells. The membrane-bound FCp6 wa s shown to generate singlet oxygen efficiently. The average cytoplasmic con centration of FCp6 in A549 cells achieved ca 80% of its extracellular conce ntration in complete medium. The dye was characterized by a very fast efflu x (16-fold decrease in 2 h), The ex vivo analysis of FCp6 fluorescence in m ice revealed that the maximal dye content in blood, tissues, organs and tum or was achieved in less than 1 h after injection, followed by a considerabl e (ca six-fold) decrease during the next 23 h and a long-term persistence a t low level. A preferential accumulation of FCp6 in subcutaneously implante d Ehrlich carcinoma along with its higher retention level comparing to the surrounding skin and muscles were observed in mice treated with different d ye doses. In vitro cytotoxic assays with A549 and Raji B-cell lymphoma cell s as well as in vivo analyses using Ehrlich carcinoma in mice revealed the very low toxicity of FCp6 without light irradiation and the significant pho todynamic activity of this compound.