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Direct Near‐infrared Luminescence Detection of Singlet Oxygen Generated by Photodynamic Therapy in Cells In Vitro and Tissues In Vivo ¶
Author(s) -
Niedre Mark,
Patterson Michael S.,
Wilson Brian C.
Publication year - 2002
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2002)0750382dnildo2.0.co2
Subject(s) - singlet oxygen , photodynamic therapy , photosensitizer , luminescence , in vivo , chemistry , photochemistry , intracellular , biophysics , photomultiplier , oxygen , optoelectronics , materials science , detector , optics , biology , biochemistry , physics , microbiology and biotechnology , organic chemistry
Singlet oxygen ( 1 O 2 ) is believed to be the major cytotoxic agent involved in photodynamic therapy (PDT). Measurement of 1 O 2 near‐infrared (NIR) luminescence at 1270 nm in biological environments is confounded by the strongly reduced 1 O 2 lifetime and probably has never been achieved. We present evidence that this is now possible, using a new NIR‐sensitive photomultiplier tube. Time‐resolved 1 O 2 luminescence measurements were made in various solutions of aluminum tetrasulphonated phthalocyanine (AlS 4 Pc) and Photofrin. Measurements were also performed on suspensions of leukemia cells incubated with AlS 4 Pc, and a true intracellular component of the 1 O 2 signal was clearly identified. Time‐resolved analysis showed a strongly reduced 1 O 2 lifetime and an increased photosensitizer triplet‐state lifetime in the intracellular component. In vivo measurements were performed on normal skin and liver of Wistar rats sensitized with 50 mg/kg AlS 4 Pc. In each case, a small but statistically significant spectral peak was observed at 1270 nm. The 1 O 2 lifetime based on photon count rate measurements at 1270 nm was 0.03–0.18 μs, consistent with published upper limits. We believe that these are the first direct observations of PDT‐generated intracellular and in vivo 1 O 2 . The detector technology provides a new tool for PDT research and possibly clinical use.