Carbohydrate Sensing Using Water-Soluble Poly(methacrylic acid)-co-3-(Acrylamido)phenylboronic Acid Copolymer

Carbohydrate and saccharide sensing in water remains very challenging. Using the covalent reversible interaction between boronic acids and the diol groups in carbohydrates is still one of the most common approaches. However, the binding affinity and solubility of isolated boronic acids are poor in water, which significantly limits their application in physiological conditions. In this work, we improved the solubility and affinity of this interaction by connecting phenylboronic acid moieties to a hydrophilic poly(methacrylic acid) (PMAA) polymer to generate a water-soluble poly(methacrylic acid)-co-3-(acrylamido)phenylboronic acid (PMAA-co-AAPBA) copolymer as a supramolecular receptor. An indicator displacement assay including oxidized hematoxylin dye was used to study the interaction of the PMAA-co-AAPBA receptor with monosaccharides (e.g., fructose, glucose, galactose, and ribose) and disaccharides (e.g., lactose, maltose, sucrose, and trehalose). Data interpretation using linear discriminant analysis (LDA) confirmed that the [PMAA-co-AAPBA·dye] complex successfully differentiated both monosaccharides and disaccharides in neutral aqueous solution. The observed binding affinity trend provided further evidence in support of the fact that boronic acids bind more efficiently to vicinal cis-diols on five-membered rings than on six-membered rings. This system demonstrates the enhanced affinity and water solubility attainable through grafting a supramolecular sensing motif to an appropriate polymeric support, with an eye to future applications in biological and environmental contexts.