IN-VITRO PHOTO-ACTIVATION OF NEWLY SYNTHESIZED CHLORIN DERIVATIVES WITH RED-LIGHT-EMITTING DIODES

We investigated the in vitro photo-activation properties of two chlori n derivatives, i.e. 8-cis-heptylchlorin dicarboxylic acid and S-trans- heptylchlorin bisamidoglucose derivative, which exhibit lipophilic pro perties similar to those of the active fractions of Photofrin II, on a normal epithelial cell line (FRTL-5). We used as an irradiation sourc e an array of diodes emitting red light (lambda = 675 nm), which produ ced a fluence of 7 mW cm(-2) on the cells. We found that photo-activat ion with chlorin derivatives in the concentration range 1-100 ng mi(-1 ) greatly enhanced the mortality of the irradiated cells (energy densi ty, 0.25 J cm(-2)) with respect to the control cells kept in the dark. This response is immediate and appears to be an 'all or none' effect. Taking into account that compounds exhibit a strong absorbance peak i n the long wavelength region of visible light where tissues are relati vely transparent, our results suggest that chlorins can be considered to be good candidates for application in photodynamic therapy. (C) 199 7 Elsevier Science S.A.