Time-resolved, total internal reflection fluorescence microscopy of cultured cells using a Tb chelate label

A total internal reflection fluorescence microscope with time-resolved spectroscopy and CCD imaging capabilities is described. The capability of the microscope to selectively detect, via temporal resolution, the presence of a long-lived luminescence label in biological cells in vitro was evaluated. Tb chelates having radiative lifetimes of ca. 1.5 ms were employed as long-lived, extrinsic labels. Microspectroscopy and imaging were performed on mouse 3T3 cells stained with Tb chelates, stained with DiI (an extrinsic membrane label of ns lifetime), and in the absence of an extrinsic label. The results demonstrate the efficiency of using time-resolved detection to discriminate against intrinsic and extrinsic sources of short-lived emission in cultured cells, which enables long-lived, extrinsic luminescence to be selectively detected. Potential applications of this technology are discussed.