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SINGLET OXYGEN GENERATION OF PORPHYRINS, CHLORINS, AND PHTHALOCYANINES
Author(s) -
Kimel S.,
Tromberg B. J.,
Roberts W. G.,
Berns M. W.
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04145.x
Subject(s) - singlet oxygen , photochemistry , chemistry , photodegradation , oxygen , phthalocyanine , singlet state , photocatalysis , organic chemistry , catalysis , physics , nuclear physics , excited state
— The production of singlet oxygen was measured indirectly for three classes of photosensitizers: porphyrins (Photofrin II, TPPS 4 ), chlorins (MACE, DACE), and a phthalocyanine (CASPc). Buffered solutions of sensitizers and singlet oxygen acceptors were irradiated with a CW dye laser and the oxygen depletion was monitored electrochemically with a Clark‐type microelectrode. A comparison of oxygen‐depletion rate constants and quantum efficiencies yields the order of efficiency of the sensitizers: TPPS 4 > MACE > PII > DACE > CASPc. For singlet oxygen acceptors the order was: furfuryl alcohol > imidazole > tryptophan. CHO cell suspensions were also used as acceptors. Here the order of efficiency (per absorbed photon) was PII > MACE = CASPc. Expressed in terms of oxygen depletion per cell the order was CASPc = PII > MACE. When performing cell clonogenicity studies the order of efficiencies, expressed as percentage cell kill per unit weight of sensitizer, was CASPc > PII > MACE = DACE. The discrepancy between the efficiencies of sensitizers to generate singlet oxygen and their cytotoxicity was explained in terms of photodegradation (for the chlorins), intracellular localization (for PII), and contributions from a Type I mechanism (for CASPc).