IN-VIVO ABSORPTION-SPECTRUM OF DISULFONATED ALUMINUM PHTHALOCYANINE IN A MURINE TUMOR-MODEL

The absorption spectrum of aluminium phthalocyanine with an average di sulphonation of 2.1 (hereafter called disulphonated aluminium phthaloc yanine, AlS(2)Pc) was measured in vivo in a murine tumour model by mea ns of time-resolved reflectance. Mice bearing the L1210 leukaemia were administered 2.5 or 5 mg/kg body weight (b.w.) of AlS(2)Pc intraperit oneally. Reflectance measurements were performed in the 650-695 nm ran ge before and 1, 4 and 7 h after the drug administration. Fitting of t he data with the diffusion theory allowed us to assess the absorption coefficient in both conditions (i.e. before and after). As a differenc e between the latter and the former data, the in vivo absorption spect rum of AlS(2)Pc was evaluated. 1 h after the administration of 2.5 mg/ kg b.w. AlS(2)Pc, the absorption peak was centred at 685 nm, red-shift ed about 15 nm with respect to the spectrum in aqueous solution. For t he lower dose, the absorption line shapes 4 and 7 h after the administ ration remained very similar. The red shift of the absorption spectrum is consistent with the therapeutic efficacy of the photodynamic thera py which was measured at 672, 685 and 695 nm, and proved to be maximum at 685 nm for both the L1210 leukaemia and the MS-2 fibrosarcoma. Wit h the higher drug dose, the absorption spectra taken from different an imals showed significant differences. In particular, in some mice the line shape was similar to that measured with 2.5 mg/kg b.w., while in other subjects it showed a broadening or a second peak at shorter wave lengths. Measurements on some animals were performed also 18 and 24 h after the injection of 5 mg/kg b.w., leading to no time evolution or t o a progressive line shape narrowing.