Synthesis and Photophysical Properties of Sulfonamidophenyl Porphyrins as Models for Activatable Photosensitizers

The ability to localize agents to specific anatomic sites remains an important aspect in designing more efficient therapeutics. Light-activated therapies, in particular, allow for the focal ablation of target tissues and cells. In order to increase the specificity of these agents, stimuli-activated systems have been developed, which are nonphototoxic in the absence of activation. To this end, we propose a novel paradigm for excited state quenching and activation based upon the direct conjugation of quenching moieties to the porphyrinic macrocycle. Model compounds, based upon meso-(p-aminophenyl)porphyrins were synthesized bearing 1 to 4 sulfonamide-linked 2,4-dinitrobenzene. The singlet oxygen and fluorescence quantum yields of these compounds were obtained and compared, as well as the kinetics of activation with relevant activating agents. In addition, methods were developed to further modify the porphyrin in order to modulate the polarity and effect conjugation to biomolecules or nanoparticulate scaffolds. These systems may prove useful in the treatment of a number of disease states, such as cancer and bacterial infection.