Fluorescent Probes for Sugar Detection.

Herein a new class of polymerisable, boronic acid monomers are presented, which are used to generate soft hydrogels capable of accurate determination of saccharide concentration. Through exploitation of the interaction of these cationic boronic acid with an anionic fluorophore, 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (pyranine), a two-component sugar-sensing system was realised. In the presence of such cationic BAs (o-BA, m-BA and p-BA), the fluorescence of pyranine becomes quenched, due to the formation of a non-fluorescent boronic acid-fluorophore complex. Upon addition of saccharides, formation of a cyclic boronate ester results in dissociation of the non-fluorescent complex and recovery of the pyranine fluorescence. The response of this system was examined in solution with common monosaccharides, such as glucose, fructose and galactose. Subsequent polymerisation of the boronic acid monomers yielded cross-linked hydrogels, which showed similar reversible recovery of fluorescence in the presence of glucose.