CHARACTERIZATION OF THE INITIAL PHOTOSENS ITIZATION OF PORPHYRIN-LIKERARE-EARTH-METAL COMPLEXES IN PHOTODYNAMIC THERAPY - ESR STUDY OF THETYPE-I MECHANISM OF FREE-RADICAL PRODUCTION

By means of ESR, we studied the photosensitization of porphyrin-like r areearth metal complex [(CO2H-APPC)Ga]Cl-2. By using 4-oxo-TEMPO as a probe and through its spin elimination, the production of cation free radical [(CO2H-APPC)Gd](radical cation) in [(CO2H-APPC)Gd]Cl-2 photose nsitization was established and moreover it might be promoted by using BNAH as a reducing agent. Through trapping O-2(radical anion) and . O H with DMPO and measuring the ESR spectra of the spin adducts of [DMPO -O-2(-)](.) and [DMPO-OH](.), the O-2(radical anion) and . OH were fou nd to be definitely generated. These results showed the presence of ox ygen radicals in [(CO2H-APPC)Gd]Cl-2 photosensitization, and shed ligh t on the type I mechanism.