ELECTRON-PARAMAGNETIC-RESONANCE EVIDENCE OF THE GENERATION OF SUPEROXIDE (O-2(CENTER-DOT-)) AND HYDROXYL ((OH)-O-CENTER-DOT) RADICALS BY IRRADIATION OF A NEW PHOTODYNAMIC THERAPY PHOTOSENSITIZER, VICTORIA-BLUE-BO
A. Viola et al., ELECTRON-PARAMAGNETIC-RESONANCE EVIDENCE OF THE GENERATION OF SUPEROXIDE (O-2(CENTER-DOT-)) AND HYDROXYL ((OH)-O-CENTER-DOT) RADICALS BY IRRADIATION OF A NEW PHOTODYNAMIC THERAPY PHOTOSENSITIZER, VICTORIA-BLUE-BO, Journal of photochemistry and photobiology.B, Biology, 32(1-2), 1996, pp. 49-58
Electron paramagnetic resonance (EPR) experiments were performed on Vi
ctoria Blue BO, a cationic dye whose photocytotoxicity has been studie
d against the human leukaemic cell lines K-562 and TF-1. EPR experimen
ts with 2,2,6,6-tetramethyl-4-piperidone and spin trapping with 5,5-di
methyl-1-pyrroline-N-oxide showed that, on illumination in aerated aqu
eous solution or DL-alpha-dipalmitoylphosphatidylcholine liposomes, ph
otoexcited Victoria Blue BO is unable to generate O-1(2), whereas O-2(
.-) and (OH)-O-. are trapped by 5,5-dimethyl-1-pyrroline-N-oxide in th
e presence or absence of electron donors. The O-2(.-) formed probably
leads to the (OH)-O-. radical, with an efficiency which is increased b
y electron donors such as Fe2+.