Monosaccharide Binding to Synthetic Carbohydrate Receptor Microarrays

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)
are controlled precisely at each feature in the array. The influence
of h and Γ on the binding to five fluorescently
labeled 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 9072 data points, each corresponding to
an individual binding experiment, which 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.