Direct near-infrared luminescence detection of singlet oxygen generated by photodynamic therapy in cells in vitro and tissues in vivo

摘要

Singlet oxygen (O-1(2)) is believed to be the major cytotoxic agent involved in photodynamic therapy (PDT). Measurement of O-1(2) near-infrared (NIR) luminescence at 1270 run in biological environments is confounded by the strongly reduced O-1(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. O-1(2) luminescence measurements were made in various solutions of aluminum tetrasulphonated phthalocyanine (AIS(4)Pc) and Photofrin. Measurements were also performed on suspensions of leukemia cells incubated with AIS(4)Pc, and a true intracellular component of the O-1(2) signal was clearly identified. Time-resolved analysis showed a strongly reduced O-1(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 AIS(4)PC. In each case, a small but statistically significant spectral peak was observed at 1270 rim. The O-1(2) lifetime based on photon count rate measurements at 1270 nm was 0.03-0.18 mus, consistent with published upper limits. We believe that these are the first direct observations of PDT-generated intracellular and in Vivo O-1(2). The detector technology provides a new tool for PDT research and possibly clinical use. [References: 32]