Monosaccharide Binding to Synthetic Carbohydrate Receptor Microarrays

A glycan detection platform, comprised of synthetic carbohydrate receptors (SCRs) immobilized onto polymer brushes, was prepared. <b>SCR043</b>, an alkene-containing SCR, was incorporated into grafted-from polymer brushes using hypersurface photolithography, resulting in microarrays of <b>SCR043</b>-functionalized polymer brushes, where brush height (<i>h</i>) and SCR grafting density (Γ) are controlled precisely at each feature in the array. The influence of <i>h</i> and Γ on the binding to five fluorescently labeled monosaccharides<i>α</i>-glucose (<b>α-Gluc-FL</b>), α-galactose (<b>α-Gal-FL</b>), α-mannose (<b>α-Man-FL</b>), β-glucose (<b>β-Gluc-FL</b>), and β-galactose (<b>β-Gal-FL</b>)in aqueous buffer was investigated using fluorescence microscopy. These experiments provided 9072 data points, each corresponding to an individual binding experiment, which were used to assess the effects of polymer <i>h</i>, Γ, monosaccharide structure, and monosaccharide concentration on binding avidity (<i>K</i> _d). We demonstrate that SCR-based microarrays bind monosaccharides selectively as a result of cooperative, supramolecular interactions that occur within the multivalent polymer brushes. <i>K</i> _d, Hill coefficients, 50% inhibition concentrations, and inhibition constants (<i>K</i> _i) were calculated for the different monosaccharide<b>-SCR043</b> binding pairs and were compared with the binding energies calculated using Density Functional Theory. The SCR-functionalized polymer brush microarrays could detect monosaccharides at micromolar concentrations in aqueous buffers, with <i>K</i> _i as low as 5 μM for <b>α-Man-FL</b>. The strength of the monosaccharide-SCR interactions is attributed to the cluster-glycoside effects that can occur within the SCR-functionalized polymer brushes. This report represents the first demonstration that SCRs can function as effective glycan recognition elements in microarray formats.