Two new sensitizers are introduced for a potential use in
photodynamic therapy: Zn(2+)- and MG(2+)-tetrabenzoporphyrin (ZnTBP and MgTBP). A comparative study of the quantum yields of
singlet oxygen generation (phi delta) of
hematoporphyrin derivative (HpD),
Photofrin II (PF-II), Zn(2+)-
phthalocyanine tetrahydroxyl [
ZnPC(OH)4] and the newly introduced sensitizers ZnTBP and MgTBP in
liposomes, as well as the kinetics of a photochemical reaction sensitized by them, was made by employing the fluorescent membrane probe
9,10-dimethylanthracene (DMA). We followed the
photosensitization of DMA in real time by monitoring its fluorescence decrease at 457 nm and found that DMA's
photosensitization is
oxygen mediated. The kinetic traces of the
photosensitization reactions were fitted to an analytical function, and the phi delta values were evaluated.
At 10 microM sensitizer in an aqueous
suspension of 2 mg/mL egg
phosphatidylcholine (
EPC), HpD was found to have the largest value of phi delta (0.215), followed by PF-II (0.191), ZnTBP (0.023), MgTBP (0.019) and
ZnPC(OH)4 (0.005). As a test of the method, phi delta for
methylene blue in
ethanol was measured and found to be 0.45 as compared to 0.52 reported in the literature. Due to difference in the sensitizers' absorbances at the
laser's wavelength, the reaction photosensitized by ZnTBP was the fastest with a time constant of 6.7 min, followed by MgTBP (8.7), PF-II (11.9), HpD (17.1) and
ZnPC(OH)4 (31.2), all at equal sensitizers' concentrations and
laser intensities. The binding constants of the sensitizers to
EPC liposomes are also reported.