Detection of total sugar concentration using photoinduced electron transfer materials: development of operationally stable, reusable optical sensors

The work presented here describes the synthesis and testing of a number of related boronic-acid containing photoinduced electron transfer (PET) materials for use in saccharide measurement. These chemicals consist of a fluorophore and boronic acid attached to an amine and show increased fluorescence on saccharide binding to the boronic acid. When the boronic acid complexes with the saccharide the boron atom becomes more acidic leading to an enhanced Lewis acid–Lewis base interaction with the amine nitrogen. This reduces the interaction of the nitrogen lone pair with the fluorophore suppressing the PET process and increasing fluorescence. The work described here investigates the effect of spacer length between two boronic acids on the same molecule, on the selectivity and sensitivity of saccharide binding. The stability of these compounds against stress from high temperatures and ionic strength has also been investigated. A second type of chemical, with a vinyl group has been synthesised and tested for saccharide measurement abilities. This chemical may be crosslinked into a polymer and enable its incorporation onto a polymer-coated optical fibre for the potential production of reusable saccharide sensors.