PHOTOPHYSICAL AND REDOX PROPERTIES OF A SERIES OF PHTHALOCYANINES - RELATION WITH THEIR PHOTODYNAMIC ACTIVITIES ON TF-1 AND DAUDI LEUKEMIC-CELLS

The photodynamic therapy (PDT) efficiency of five phthalocyanines, chl oroaluminum phthalocyanine (AIPc), dichlorosilicon phthalocyanine (SiP c), bis(tri-n-hexylsiloxy)silicon phthalocyanine (PcHEX), bis(tripheny lsiloxy)silicon phthalocyanine (PcPHE) and nickel phthalocyanine (NiPc ), was assessed on two leukemic cell lines TF-1 and erythroleukemic an d B lymphoblastic cell lines, Daudi, respectively, AIPc showed the bes t photocytotoxicity leading to 0.008 surviving fraction at 2 x 10(-9) M for TF-1 and 4 x 10(-9) M for Daudi, At 5 x 10(-7) M, SiPc and PcHEX induced a significant photokilling, whereas NiPc and PcPHE were inact ive, Laser flash photolysis and photoredox properties of the phthalocy anines were investigated to try to relate these parameters with the bi ological effects, AIPc showed the longest triplet lifetime: 484 mu s i n dimethyl sulfoxide/H2O. This value was increased up to 820 mu s when AIPc was complexed with human serum albumin used as a membrane model, Such an enhancement was not observed with the silicon phthalocyanines . Upon irradiation, all the phthalocyanines generated singlet oxygen w ith 0.29-0.37 quantum yield values, The reduction potentials of the ex cited states obtained from measurement in the ground state and energy of the excited triplets show that AIPc is the best electron acceptor. The in vitro photocytotoxicity observed and the measured parameters ar e in agreement with a key role of electron transfer in PDT assays invo lving these phthalocyanines.