Effect of Adriamycin treatment on the lifetime of pyrene butyric acid in single living cells

We investigated the fluorescence lifetime of pyrene butyric acid (PBA) using various O2 concentrations in cells. Both in living and freshly fixed cells, PBA lifetime decreased with oxygen concentration. We recorded decay curves in single cells and measured PBA lifetime and NAD(P)H intensity values. Under nitrogen atmosphere, the probe lifetime differences (199 and 209 ns in living and freshly fixed cells, respectively) suggest a supplemental pathway for the deactivation of the probe when the cell functions are not stopped. We propose reactive oxygen species (ROS) to be the additional quenchers that cause this decrease. We further studied the effect of drugs generating ROS the anthracycline doxorubicin (adriamycin). For living cells, PBA lifetime decreased after adriamycin (ADR) treatment (200 and 1000 ng/ml). This supports our hypothesis that under nitrogen atmosphere and for freshly fixed cells, PBA lifetimes increase to an unchanging value due to absence of quenchers.