Two-photon absorption of copper tetrasulfophthalocyanine induces phototoxicity towards Jurkat cells in vitro.

The feasibility to induce oxygen-independent tumour cell kill by two-photon excitation of copper tetrasulfophthalocyanine (CuPcS4) was studied in Jurkat cells in vitro. Following incubation with CuPcS4 cells were transferred to a closed cuvette and irradiated with 532 nm pulsed-laser or 680 nm continuous-laser light to evaluate the effect of either two- or one-photon excitation, respectively. Cell survival was measured using MTT and Trypan Blue exclusion tests. Cell viability decreased 10-20% following two-photon excitation while one-photon illumination did not affect cell survival. These data confirm that two-photon excitation of CuPcS4 to the upper excited triplet state results in the formation of toxic species suggesting its potential use as a sensitizer for the photodynamic treatment of poorly oxygenated tumours.