Monosaccharide Binding to Synthetic Carbohydrate Receptor Microarrays

Abstract

Chapter 1: A glycan detection platform comprised of synthetic carbohydrate receptors (SCRs) immobilized onto polymer brushes was prepared. SCR043, an alkene-containing SCR, was incorporated into grafted-from polymer brushes using hypersurface photolithography, resulting in microarrays of SCR043-functionalized polymer brushes, where brush height (h) and SCR grafting density (Γ) is controlled precisely at each feature in the array. The influence of h and Γ on the binding to five fluorescently labelled monosaccharides – α-glucose (α-Gluc-FL), α-galactose (α-Gal-FL), α-mannose (α-Man-FL), β-glucose (β-Gluc-FL), and β-galactose (β-Gal-FL) – in aqueous buffer was investigated using fluorescence microscopy. These experiments provided 9,072 data points, each corresponding to an individual binding experiment that were used to assess the effects of polymer h, Γ, monosaccharide structure, and monosaccharide concentration on binding avidity (Kd). We demonstrate that SCR-based microarrays bind monosaccharides selectively as a result of cooperative, supramolecular interactions that occur within the multivalent polymer brushes. Kd, Hill coefficients, 50% inhibition concentrations, and inhibition constants (Ki) were calculated for the different monosaccharide-SCR043 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 Ki as low as 5 μM for α-Man-FL. 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