A facile method for the preparation of gold glyconanoparticles from free oligosaccharides and their applicability in carbohydrate-protein interaction studies

The weak binding affinity of monomeric oligosaccharides with carbohydrate-binding proteins are hampering their use in in-vivo and in-vitro bio-assays. Gold glyconanoparticles (GNPs), prepared from synthetic oligosaccharides, have been used to overcome this weak binding affinity. In this paper, a convenient method for the preparation of GNPs from free oligosaccharides is presented. The reductive animation of saccharides with trityl-protected cysteamine, followed by detritylation, afforded cysteamine-extended saccharides that could be used for the preparation of GNPs under reducing conditions in water. The robust chemistry and facile purification of intermediate and final compounds ensure high yields and reproducible results and the, subsequent, preparation of GNPs proceeded smoothly, even with minute quantities (nanomolar scale) of the cysteamine-extended saccharide. The described method was used to synthesize a series of gluco- and manno-oligosaccharide-containing GNPs. The prepared GNPs were validated in interaction studies with Con A, using either surface plasmon resonance (SPR), UV/ Vis spectroscopy, or transmission electron microscopy (TEM). The described method for the preparation of water-soluble gold glyconanoparticles can be used for the identification of carbohydrate ligands for novel carbohydrate-binding proteins, and can find application as inhibitors of pathological interactions. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).