Quantitative in vitro demonstration of two-photon photodynamic therapy using photofrin and visudyne.

Khurana, M; Collins, H; Karotki, A; Anderson, H; Cramb, D; Wilson, B

Journal article

Quantitative in vitro demonstration of two-photon photodynamic therapy using photofrin and visudyne.

Abstract:: Photodynamic therapy (PDT), the combined action of a photosensitizer and light to produce a cytotoxic effect, is an approved therapy for a number of diseases. At present, clinical PDT treatments involve one-photon excitation of the photosensitizer. A major limitation is that damage may be caused to healthy tissues that have absorbed the drug and lie in the beam path. Two-photon excitation may minimize this collateral damage, as the probability of absorption increases with the square of the light intensity, enabling spatial confinement of the photosensitizer activation. A potential application is the treatment of the wet-form of age-related macular degeneration, the foremost cause of central vision loss in the elderly. Herein, the commercial photosensitizers Visudyne and Photofrin are used to demonstrate quantitative in vitro two-photon PDT. A uniform layer of endothelial cells (YPEN-1) was irradiated with a Ti:sapphire laser (300 fs, 865 nm, 90 MHz) using a confocal scanning microscope. Quantification of the two-photon PDT effect was achieved using the permeability stain Hoechst 33258 and a SYTOX Orange viability stain. Visudyne was found to be around seven times more effective as a two-photon photosensitizer than Photofrin under the conditions used, consistent with its higher two-photon absorption cross-section. We also demonstrate for the first time the quadratic intensity dependence of cellular two-photon PDT. This simple in vitro method for quantifying the efficacy of photosensitizers for two-photon excited PDT will be valuable to test specifically designed two-photon photosensitizers before proceeding to in vivo studies in preclinical animal models.

Publication status:: Published

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APA Style

Khurana, M., Collins, H., Karotki, A., Anderson, H., Cramb, D., & Wilson, B. (2007). Quantitative in vitro demonstration of two-photon photodynamic therapy using photofrin and visudyne. Photochemistry and Photobiology, 83(6), 1441–1448.

MLA Style

Khurana, M, et al. “Quantitative in Vitro Demonstration of Two-Photon Photodynamic Therapy Using Photofrin and Visudyne.” Photochemistry and Photobiology, vol. 83, no. 6, 2007, pp. 1441–48.

Chicago Style

Khurana, M, H Collins, A Karotki, H Anderson, D Cramb, and B Wilson. 2007. “Quantitative in Vitro Demonstration of Two-Photon Photodynamic Therapy Using Photofrin and Visudyne.” Photochemistry and Photobiology 83 (6): 1441–48.
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