Theranostics 2012; 2(9):817-826. doi:10.7150/thno.4479

Research Paper

Monitoring Photosensitizer Uptake Using Two Photon Fluorescence Lifetime Imaging Microscopy

Shu-Chi Allison Yeh1, Kevin R. Diamond3, Michael S. Patterson1,3, Zhaojun Nie1, Joseph E. Hayward2,3, Qiyin Fang1,2,✉

1. School of Biomedical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada;
2. Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada;
3. Department of Medical Physics and Applied Radiation Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada.

Abstract

Photodynamic Therapy (PDT) provides an opportunity for treatment of various invasive tumors by the use of a cancer targeting photosensitizing agent and light of specific wavelengths. However, real-time monitoring of drug localization is desirable because the induction of the phototoxic effect relies on interplay between the dosage of localized drug and light. Fluorescence emission in PDT may be used to monitor the uptake process but fluorescence intensity is subject to variability due to scattering and absorption; the addition of fluorescence lifetime may be beneficial to probe site-specific drug-molecular interactions and cell damage. We investigated the fluorescence lifetime changes of Photofrin® at various intracellular components in the Mat-LyLu (MLL) cell line. The fluorescence decays were analyzed using a bi-exponential model, followed by segmentation analysis of lifetime parameters. When Photofrin® was localized at the cell membrane, the slow lifetime component was found to be significantly shorter (4.3 ± 0.5 ns) compared to those at other locations (cytoplasm: 7.3 ± 0.3 ns; mitochondria: 7.0 ± 0.2 ns, p < 0.05).

Keywords: Fluorescence lifetime imaging microscopy (FLIM), Photodynamic Therapy (PDT), Photofrin, Segmentation.

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How to cite this article:
Yeh SCA, Diamond KR, Patterson MS, Nie Z, Hayward JE, Fang Q. Monitoring Photosensitizer Uptake Using Two Photon Fluorescence Lifetime Imaging Microscopy. Theranostics 2012; 2(9):817-826. doi:10.7150/thno.4479. Available from http://www.thno.org/v02p0817.htm