This study include in the same frame promising structures tailored as photoactive agents for photodynamic therapy of cancer versus one of the most versatile cell lines from experimental point of view, fibroblasts type, subcutaneous connective tissues- L929. Transmembrane potential was studied establishing important features in the behavior of chemical vectors against cultured cells via membranar media. Two amphiphilic porphyrins, 5,15-bis-(4-hydroxy-3-methoxyphenyl)-10,20-bis-(4-carboxymethylphenyl)porphyrin and Zn(II)-5,15-bis-(4-hydroxy-3-methoxyphenyl)-10,20-bis-(4-carboxymethylphenyl)porphyrin were assessed in terms of the effect on membrane potential. The comparative effect of free base porphyrin and metalloporphyrin with amphiphilic structure, reveal hyperpolarization phenomena and bring informations about consequences of active compound concentration against cell membrane.