Two-photon excitation of chlorin-e 6 -C 15 monomethyl ester for photodynamic therapy

Abstract

Two-photon-induced fluorescence spectrum and lifetime of Chlorin-e₆-C₁₅ Monomethyl Ester in tetrahydrofura (THF) are experimentally examined with femtosecond laser pulses at 800 nm from a Ti:sapphire laser. The two-photon excited fluorescence spectra of the molecule are basically similar to those obtained by one-photon excitation. The lifetimes of two-photon and one-photon excitation fluorescence of this molecule in the solution are of the order of 5.2 ns and 4.8 ns respectively. Our experimental results indicate that the two-photon-induced photodynamic processes of Chlorin-e₆-C₁₅ Monomethyl Ester are similar to one-photon-induced photodynamic processes. The two-photon absorption cross section of the molecule is measured at 800 nm as about σ₂^' ≈ 29.1 x 10^-50 cm⁴ • s/photon. As an example for two-photon photodynamic therapy, we also further examine the cell-damaging effects of the Ester. Our preliminary results of cell viability test indicate that Chlorin-e₆-C₁₅ Monomethyl Ester can effectively damage the liver cancer cells BEL-7402 under two-photon irradiation. Our results suggest Chlorin-e₆-C₁₅ Monomethyl Ester may become a potential two-photon phototherapeutic agent.