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Journal of Biomedical Optics

Fluorescence detection of protoporphyrin IX in living cells: a comparative study on single- and two-photon excitation
Author(s): Sijia Lu; Ji Yao Chen; Yu Zhang; Jiong Ma; Pei Nan Wang; Qian Peng
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Paper Abstract

Photodynamic therapy (PDT) involves a combination of a lesion-localizing photosensitizer with light and has been established as a new modality for some medical indications. Much evidence has shown the correlation between subcellular localization of a photosensitizer with its photodynamic efficiency. However, the fluorescence of most photosensitizers in cells is weak and easily photobleached. We compare the effect of single-photon excitation (SPE) with that of two-photon excitation (TPE) on fluorescence detection of protoporphyrin IX (PpIX), a potent photosensitizer, in the PLC hepatoma cells in vitro. By using laser scanning confocal fluorescence microscopy, both fluorescence images and spectra of intracellular PpIX are studied with SPE of 405- and 488-nm lasers, and TPE of 800-nm femtosecond laser. The 405-nm laser is more efficient at exciting PpIX fluorescence than the 488-nm laser, but causes a considerable photobleaching of the PpIX fluorescence and induces weak autofluorescence signals of native flavins in the cells as well. The 800-nm TPE is found to significantly improve the quality of PpIX fluorescence images with negligible PpIX photobleaching and minimized endogenous autofluorescence, indicating the potential of 800-nm TPE for studying cellular localization of porphyrin photosensitizers for PDT.

Paper Details

Date Published: 1 March 2008
PDF: 5 pages
J. Biomed. Opt. 13(2) 024014 doi: 10.1117/1.2907316
Published in: Journal of Biomedical Optics Volume 13, Issue 2
Show Author Affiliations
Sijia Lu, Fudan Univ. (China)
Ji Yao Chen, Fudan Univ. (China)
Yu Zhang, Fudan Univ. (China)
Jiong Ma, Fudan Univ. (China)
Pei Nan Wang, Fudan Univ. (China)
Qian Peng, Univ. of Oslo (Norway)


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