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Journal of Biomedical Optics

Effect of liposomal confinement on photothermal and photo-oximetric fluorescence lifetimes of photosensitizers with varying hydrophilicity
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Paper Abstract

The time-resolved fluorescence of photosensitizers (PSs) of varying hydrophobicities, di-and tetrasulfonated Al phthalocyanines (Al-2 and Al-4), and Photochlor® (HPPH), was investigated in liposomes used as cell-mimetic models. Using frequency-and time-domain apparatus, the fluorescence lifetime, τ fluo, was compared for PSs free in aqueous solution and in a liposome-associated state at varied temperatures (25 to 78°C) and oxygen concentrations (0–190 μM). The analysis of τ fluo revealed different decay behaviors for the free-solution and liposome-confined PSs, most significantly for the lipophilic HPPH. Hydrophilic PS drugs (Al-4, Al-2) were less affected by the liposomal confinement, depending on the relative hydrophilicity of the compound and the consequent localization in lipsomes. Changes in the emission decay due to confinement were detected as differences in the lifetime between the bulk solution and the liposome-localized PS in response to heating and deoxygenation. Specifically, hydrophilic Al-4 produced an identical lifetime trend as a function of temperature both in solu and in a liposome-confined state. Hydrophobic HPPH exhibited a fundamental transformation in its fluorescence decay kinetics, transitioning from a multiexponential (in free solution) to single-exponential (in liposome) decay. Deoxygenation resulted in a ubiquitous τ fluo increase for all PSs in free solution, while the opposite, a τ fluo decrease, occurred in all liposomal PSs.

Paper Details

Date Published: 1 July 2008
PDF: 11 pages
J. Biomed. Opt. 13(4) 041314 doi: 10.1117/1.2952298
Published in: Journal of Biomedical Optics Volume 13, Issue 4
Show Author Affiliations
Ozzy Mermut, Institut National d'Optique (Canada)
Isabelle Noiseux, Institut National d'Optique (Canada)
Jean-Pierre Bouchard, Institut National d'Optique (Canada)
Jean-François Cormier, Institut National d'Optique (Canada)
Patrice Desroches, Institut National d'Optique (Canada)
Michel Fortin, Institut National d'Optique (Canada)
Pascal Gallant, Institut National d'Optique (Canada)
Sébastien Leclair, Institut National d'Optique (Canada)
Marcia L. Vernon, Institut National d'Optique (Canada)
Kevin R. Diamond, Juravinski Cancer Ctr. (Canada)
Michael S. Patterson, Juravinski Cancer Ctr. (Canada)

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