Oxygen concentration imaging in a single living cell using phosphorescence lifetime of Pt-porphyrin

Abstract

An oxygen concentration imaging system inside a single living cell, based on the phosphorescence lifetime, under a microscope was developed. A fluorescence microscope equipped with a pulsed Nd : YAG laser (532 nm) and a CCD camera equipped with a gated imaging intensifier was used. When the cell was incubated with the phosphorescent compound, platinum tetra-(carboxyphenyl)-porphyrin ( PtTCPP ) was incorporated and localized in the cell. As the phosphorescence intensity depends not only on the concentration of a quencher such as oxygen but also on the concentration of phosphorescent molecules, the oxygen concentration was measured by the phosphorescence lifetime. To measure the oxygen concentration image, the time dependence of the phosphorescence intensity was observed under a microscope. The phosphorescence intensity decay obeyed first order kinetics and the oxygen concentration imaging in the single cell was obtained by the lifetime of a single exponential decay curve.