Photodynamic effect of metallo 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl) porphyrins in biomimetic AOT reverse micelles containing urease

The photodynamic effect of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl) porphyrin (H2P) and its metal complex with Zn(II), Pd(II), Cu(II) and Ni(II) has been compared in homogeneous medium and in reverse micelles of n-heptane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water bearing urease as biological substrate model. The formation of porphyrin metal complex produces changes mainly in the free-base porphyrin characteristic absorption Q-bands and in the fluorescence quantum yields (φF). The singlet molecular oxygen, O2(1Δg), production was evaluated using 9,10-dimethylanthracene (DMA) in tetrahydrofuran (THF) yielding values of ΦΔ ∼0.48, 0.77 and 0.88 for H2P, ZnP and PdP, respectively. DMA decomposition was not observed using CuP and NiP as sensitizer. The addition of β-carotene (Car) suppresses the O2(1Δg)-mediated photooxidation of DMA. The photodynamic effect of these porphyrins on the urease activity was evaluated in water and in AOT reverse micelles. In both media, the enzyme photoinactivation increases with the sensitizer O2(1Δg) production. Also, the addition of azide ion photoprotects the urease activity. Therefore, the O2(1Δg) mediation appears to be mainly responsible for the enzyme inactivation in these media. The behavior of amphiphilic porphyrins in biomimetic microenvironments provides evidences about the promissory activity of these agents in photodynamic therapy (PDT).