Chemical sensing based on fluorescence is presently undergoing rapid development. As one example, fluorescence lifetime measurements are now being used for measuring cation and anion concentrations in clinical chemistry, cellular imaging and flow cytometry. Additionally, there is an increasing use of proteins as sensors because of their high affinity and specificity for ligands.

In this report we describe some recently developed approaches to fluorescence sensing. These new methods are based on the use of a fluorescence reference either within the sample or external to the sample, but within the optical path. Two types of references are used; microsecond lifetime metalligand complexes (MLCs) or oriented films of ns decay time fluorophores. A protein sensor for glucose was developed using the glucose-galactose binding protein (GGBP) from E.coli (Figure 1).