A macrocyclic fluorescent probe for the detection of citrate

We present a macrocyclic fluorescent probe for the detection of citrate. This receptor binds citrate through hydrogen-bonding interactions in aqueous solutions, and exhibits a turn-on in fluorescence in response to binding. The presence of common biologically relevant dicarboxylate species does not significantly impact the fluorescence response. We have demonstrated the utility of this probe with the staining of murine splenocytes, and identified different basal levels of citrate present in immune cell subsets via flow cytometry analysis. A macrocycle that contains multiple hydrogen bond donors provides a selective 'turn-on' fluorescence response upon binding to citrate in aqueous media.