Glycan gold nanoparticles as a multifunctional probe for dissecting binding mechanism of concanavalin A

Multivalent lectin-glycan interactions play a significant role in biology. Developing novel methods to investigate glycosyl-receptor interactions quantitatively and elucidate binding modes is crucial for advancing biomedical detection techniques and innovative therapeutic approaches. Herein, a mannobiose-chalcone disulfide ligand (2S-DiMan) was designed and synthesized. Through click chemistry and surface ligand exchange, 2S-DiMan-functionalized gold nanoprobes (2S-DiMan-AuNPs) were prepared and characterized. Density functional theory (DFT) calculations and molecular docking revealed that the oxygen atoms of the mannobiose moiety in 2S-DiMan have the highest negative charge, enabling specific recognition of the carbohydrate recognition domain (CRD) of concanavalin A (Con A) by effectively occupying its sugar-binding site and forming hydrogen bonds. Thus, the 2S-DiMan ligand exhibits strong binding affinity for Con A. The effect of fluorescence quenching on the recognition of Con A was further investigated. Obvious quenching was observed upon 2S-DiMan-AuNPs addition. The probes showed a dissociation constant (Kd) of 0.76 μM for Con A (affinity enhancement factor β = 315-fold vs. monovalent mannose) and achieved a limit of detection as low as 5.02 nM. This work provides a novel structure and method for analysing lectins with sugar-binding sites, investigating protein-glycan multivalent binding affinity, and assaying disease-associated glycans, with promising potential for medical research and biotechnological applications.