Allosteric Fluorescent Detection of Saccharides and Biomole-cules in Water from a Boronic Acid Functionalized Arene Ru-thenium Assembly Hosting Fluorescent Dyes.

A water-soluble arene-ruthenium metalla-rectangle (MR1) functionalized with boronic acid groups was used to host vari-ous fluorescent dyes (fluorescein, eosin Y, erythrosin B). These simple host-guest systems partially quench the natural fluorescence of the dyes, which can be regained in the presence of saccharides, phosphorylated molecules, as well as other analytes. The intensity of the regained fluorescence is directly linked to the nature of the analyte, and it shows some dose-response relationships with saccharides and phosphorylated molecules that are not compatible with a displacement assay, thus suggesting an allosteric mechanism. Interestingly, when fluorescein is trapped by the metalla-rectangle in the presence of D-fructose, half of the maximum fluorescence intensity is recovered at a fructose concentration of 17.2 ± 4.7 μM, while for D-glucose a concentration of 50.6 ± 2.5 μM is required for the same effect. Indeed, all combinations of ana-lyte-host-dye (7 analytes, 1 host, 3 dyes) show a unique dose-response relationship in water at pH 8.0. However, in the presence of naphthalene and pyrene, fluorescein⸦MR1 shows a different behavior, acting as an indicator displacement assay with full recovery of fluorescence. All data were analyzed by unsupervised machine learning technologies (PCA, cluster analysis), suggesting that such systems with multiple analyte-response behaviors are offering new perspectives for the development of highly sensitive, easily tunable, water-soluble fluorescent-based sensing arrays for biomolecules and other analytes.