Abstract
Molecular oxygen is one of the most important and a key molecule in aerobic organism. Recently, we reported that red phosphorescent iridium(III) complexes (BTP, BTPDM1) can be used as an optical probe for visualizing the oxygen levels of living cells and tissues. Here, we present the evaluation of the quantitative analysis of oxygen in living cells and tissues based on the phosphorescence lifetime measurements of BTPDM1 by using time-correlated single-photon counting (TCSPC) system. We measured the phosphorescence decay profiles of BTPDM1 delivered in the normal and tumor tissues of tumor-bearing mice by using a bifurcated fiber combined with the TCSPC system. The decay profiles of both tissues could be analyzed by double exponential decay functions. The average decay lifetime of the tumor tissue was remarkably increased as compared with that of the extratumor tissue, showing the lower oxygen levels of the tumor tissues. Based on the calibration curve constructed by using cultured cells, the oxygen levels of tumor and extratumor tissues were evaluated to be 6.1 and 50 mmHg, respectively.
