Synthesis and Biological Properties of Mannosylated Starburst Poly(amidoamine) Dendrimers

Abstract

Starburst PAMAM dendrimers ending with mannopyranoside residues were readily synthesized in large scale and good yields from commercially available dendrimers bearing high-density amine functionality on their surface and p-isothiocyanatophenyl 2,3,4,6-tetra-O-acetyl-α-d-mannopyranoside. The first four generations of this novel class of monodispersed neoglycoconjugates having up to 32 mannoside units were evaluated as ligands for the phytohemagglutinins from concanavalin A (Con A) and Pisum sativum (pea lectin) using enzyme-linked lectin assay (ELLA) and turbidimetric analyses. The binding properties of these glycodendrimers, together with reference monosaccharides, were determined using yeast mannan as a coating antigen and peroxidase-labeled lectins. These mannosylated dendrimers were demonstrated to be potent inhibitors with IC₅₀ values 400 times better than those of monomeric methyl α-d-mannopyranoside taken as a standard. Their lipophilic character was shown to be sufficient for their direct use as coating antigens in microtiter plate assays. Moreover, their ability to bind and form insoluble carbohydrate−lectin complexes was also demonstrated by radial double immunodiffusion and turbidimetric analyses. Furthermore, the ability of these ligands to selectively precipitate a mannose-binding protein (Con A) from a crude lectin mixture was also demonstrated using polyacrylamide gel electrophoresis (SDS−PAGE). These multivalent neoglycoconjugates were shown to constitute novel biochromatography materials of high affinity for the easy isolation of carbohydrate-binding proteins.