Long-lifetime green-emitting Tb

Abstract

The present report describes a new approach to stain bacteria by means of rare earth complexes. We demonstrate with selected Gram-negative and positive bacteria (Escherichia coli, Micrococcus luteus, Bacillus megaterium) that these microbes can be stained efficiently with derivatives of N-phenylanthranilic acid, flufenamic acid in particular, and Tb3+ ions. Hence, the inherent advantages of rare earth complexes, e.g. strong optical absorption (>50 000 L × M−1 × cm−1) due to the antenna effect, large Stokes’ shifts (~10 000 cm−1) and very long emission decay times (millisecond range), and, not least, enhanced photostability can be fully exploited in fluorescence microscopy and spectroscopy of the bacteria; foreseeably, these findings will also be useful in flow cytometry and ELISA techniques.