An explanation to the high efficiency of m-THPC (tempor-fin) used in photodynamic therapy

Meso-tetrahydroxylphenyl chlorin (m-THPC) is one of the most efficient prospective sensitizers used in photodynamic therapy (PDT). ESR spectroscopy, fluorescence quenching experiments and cyclic voltammogram measurement were used to study its redox properties. The results showed that the ability of m-THPC generating su-peroxide radical anions was very strong, and the rate constant of m-THPC fluorescence quenching by oxygen kq (O2)=1.46×l010 mol-1 . s-1. The values of fluorescence quenching rate constant of m-THPC by some other electron acceptors, such as methyl viologen (MV2+) and anthraquinone (An), were also measured. And they were kq, (MV2+)=5.51×l09 mol-1 . s-1, kq (An)=7.81×l09 mol-1 .s-1. The oxidation potential of m-THPC was examined to be +0.62 V (vs. NHE) in acetonitrile. All these suggested that m-THPC should be a much stronger electron donor than photofrin, the currently used in clinical photodrug, and may react easily through electron transfer with biological matter to yield various

Meso-tetrahydroxylphenyl chlorin (m-THPC) is one of the most efficient prospective sensitizers used in photodynamic therapy (PDT). ESR spectroscopy, fluorescence quenching experiments and cyclic voltammogram measurement were used to study its redox properties. The results showed that the ability of m-THPC generating superoxide radical anions was very strong, and the rate constant ofm-THPC fluorescence quenching by oxygenk q (O2)=1.46×1010 mol?1 · s?1. The values of fluorescence quenching rate constant of m-THPC by some other electron acceptors, such as methyl viologen (MV2+) and anthraquinone (An), were also measured. And they were kq(MV2+)=5.51×109 mol?1 · s?1, kq (An)=7.81×109 mol?1 · s?1. The oxidation potential ofm-THPC was examined to be +0.62 V (vs. NHE) in acetonitrile. All these suggested thatm-THPC should be a much stronger electron donor than photofrin, the currently used in clinical photodrug, and may react easily through electron transfer with biological matter to yield various radicals. So it seemed reasonable that the type I reaction may play an important role in the high activity ofm-THPC-PDT.