Synthesis of glycopolymers for microarray applications via ligation of reducing sugars to a poly(acryloyl hydrazide) scaffold

Abstract

In this paper, we report on a general synthetic strategy for the assembly of glycopolymers that capitalizes on the intrinsic reactivity of reducing glycans toward hydrazides to form stable cyclic N-glycosides. We developed a poly(acryloyl hydrazide) (PAH) scaffold to which we conjugated a variety of reducing glycans ranging in structure from simple mono- and disaccharides to considerably more complex human milk and blood oligosaccharides. The conjugation proceeds under mild conditions with excellent ligation efficiencies and in a stereoselective manner, providing glycopolymers with pendant glycans accommodated mostly in their cyclic beta-glycosidic form. Utilizing a biotin-terminated PAH scaffold prepared via RAFT polymerization, we quickly assembled a panel of glycopolymers that we microarrayed on streptavidin-coated glass. We then demonstrated that in these microarrays, the glycopolymer ligands bind lectins according to the structures of their pendant glycans. Importantly, glycopolymers containing biologically relevant branched oligosaccharides, such as sialyl Lewis(x), as well as sulfated glycosaminoglycan-like epitopes can be readily prepared using our methodology.

Scheme 1. Synthesis of Glycopolymers 5

Figure 1

Assembly of glycopolymers with complex glycans and microarray display. (A) Conjugation of human milk and blood oligosaccharides (ligation efficiencies based on glycan stoichiometry). (B) Microarrays of glycopolymers 5a−r on streptavidin-coated glass stained with Cy5-conjugated ConA, RCA I, HPA, and AAL lectins.