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Journal of Biomedical Optics • Open Access

Red versus blue light illumination in hexyl 5-aminolevulinate photodynamic therapy: the influence of light color and irradiance on the treatment outcome in vitro
Author(s): Linda Helander; Hans E. Krokan; Anders Johnsson; Odrun A. Gederaas; Kristjan Plaetzer

Paper Abstract

Hexyl 5-aminolevulinate (HAL) is a lipophilic derivative of 5-aminolevulinate, a key intermediate in biosynthesis of the photosensitizer protoporphyrin IX (PpIX). The photodynamic efficacy and cell death mode after red versus blue light illumination of HAL-induced PpIX have been examined and compared using five different cancer cell lines. LED arrays emitting at 410 and 624 nm served as homogenous and adjustable light sources. Our results show that the response after HAL-PDT is cell line specific, both regarding the shape of the dose-survival curve, the overall dose required for efficient cell killing, and the relative amount of apoptosis. The ratio between 410 and 624 nm in absorption coefficient correlates well with the difference in cell killing at the same wavelengths. In general, the PDT efficacy was several folds higher for blue light as compared with red light, as expected. However, HAL-PDT624 induced more apoptosis than HAL-PDT410 and illumination with low irradiance resulted in more apoptosis than high irradiance at the same lethal dose. This indicates differences in death modes after low and high irradiance after similar total light doses. From a treatment perspective, these differences may be important.

Paper Details

Date Published: 8 August 2014
PDF: 9 pages
J. Biomed. Opt. 19(8) 088002 doi: 10.1117/1.JBO.19.8.088002
Published in: Journal of Biomedical Optics Volume 19, Issue 8
Show Author Affiliations
Linda Helander, Norwegian Univ. of Science and Technology (Norway)
Hans E. Krokan, Norwegian Univ. of Science and Technology (Norway)
Anders Johnsson, Norwegian Univ. of Science and Technology (Norway)
Odrun A. Gederaas, Norwegian Univ. of Science and Technology (Norway)
Kristjan Plaetzer, Univ. Salzburg (Austria)


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