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Anticancer phototherapy using activation of E-combretastatins by two-photon-induced isomerization.

Journal of biomedical optics (2014-10-28)
Kathrin M Scherer, Roger H Bisby, Stanley W Botchway, John A Hadfield, Anthony W Parker
ABSTRACT

The photoisomerization of relatively nontoxic E-combretastatins to clinically active Z-isomers is shown to occur in solution through both one- and two-photon excitations at 340 and 625 nm, respectively. The photoisomerization is also demonstrated to induce mammalian cell death by a two-photon absorption process at 625 nm. Unlike conventional photodynamic therapy (PDT), the mechanism of photoisomerization is oxygen-independent and active in hypoxic environments such as in tumors. The use of red or near-infrared (NIR) light for two-photon excitation allows greater tissue penetration than conventional UV one-photon excitation. The results provide a baseline for the development of a novel phototherapy that overcomes nondiscriminative systemic toxicity of Z-combretastatins and the limitations of PDT drugs that require the presence of oxygen to promote their activity, with the added benefits of two-photon red or NIR excitation for deeper tissue penetration.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Propidium iodide, ≥94.0% (HPLC)
Sigma-Aldrich
Propidium iodide solution, solution (1.0 mg/ml in water)
Sigma-Aldrich
Nitrogen, ≥99.998%