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, chloroaluminum phthalocyanine (AIPc), dichlorosilicon phthalocyanine (SiPc), bis(tri-n-hexylsiloxy)silicon phthalocyanine (PcHEX), bis(triphenylsiloxy)silicon phthalocyanine (PcPHE) and nickel phthalocyanine (NiPc), was assessed on two leukemic cell lines TF-1 and erythroleukemic and B lymphoblastic cell lines, Daudi, respectively, AIPc showed the best 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 inactive, Laser flash photolysis and photoredox properties of the phthalocyanines were investigated to try to relate these parameters with the biological effects, AIPc showed the longest triplet lifetime: 484 mu s in 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 with 0.29-0.37 quantum yield values, The reduction potentials of the excited 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 are in agreement with a key role of electron transfer in PDT assays involving these phthalocyanines.