PHOTOPHYSICS AND INTRACELLULAR-DISTRIBUTION OF A BORONATED PORPHYRIN PHOTOTHERAPEUTIC AGENT

The absorption and emission spectra, fluorescence quantum yields and l ifetimes and triplet state properties of a boronated porphyrin, the te trakiscarborane carboxylate ester of 2,4-(alpha,beta-dihydroxyethyl) d euteroporphyrin IX (BOPP), have been determined, This compound is an a lternative photodynamic therapy (PDT) agent that exhibits highly selec tive tumor localization, with the potential to be used in conjunction with boron neutron capture therapy, The photophysical characteristics of BOPP are similar to other porphyrins and it exhibits marked aggrega tion and acid-base speciation under typical physiological conditions, In particular, protonation of the porphyrin imino (-N=) nitrogens occu rs in the pH 5-7 region and influences the photophysical properties, T ime-resolved confocal fluorescence imaging of the intracellular distri bution of BOPP in C6 glioma cells indicates distinct subcellular local ization and heterogeneity of emission. The results are interpreted and discussed in terms of the possible mechanisms for cellular uptake and localization.