Biomolecule based fluorescent sensors for the selective detection of uranium in different oxidation states

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The detection of uranium and uranyl in natural aqueous environments is absolutely paramount in deciphering and monitoring migration behavior, which in turn is crucial in cleaning up contaminated land sites and assuring the safety case of long-term geological disposal. Currently there are no examples of fluorescence based sensors for the selective detection of uranium, despite the fact that sensors for other toxic metal ions (e.g. Hg) are commonplace and now used in the environmental sampling industry. We propose that by combining selective complexation with indirect fluorescence detection systems, uranium can be detected at levels required for monitoring. A range of chemical and biochemical fluorescent probes for the ratiometric and specific detection of uranyl(VI) and uranium(IV) ions for potential use in nuclear decommissioning and environmental remediation are being developed. Specifically, this project involves the synthesis of a family of transition polypyridyl complexes of Re(I), Ru(II), Ir(III) and Pt(II) appended with a binding site for uranyl(VI), here catechol, polyaminocarboxylate and glycol, evaluating the emission response and Stern-Volmer kinetics in the presence of increasing concentrations of uranium. An attenuation in the phosphorescence of the transition metal complexes is observed due to photoinduced electron transfer. Ratiometric probes based on these constructs with two different transition metal complexes will then be constructed and the phosphorescence quenching in the presence of uranium evaluated. The project is also developing uranyl(VI) fluorescent probes using modified calcium binding proteins where uranium acts as a calcium mimic. By engineering such proteins with two fluorescent dyes, upon binding with uranyl(VI), a different fluorescence response is observed compared to addition of calcium and other common metal ions.