AuNPs were prepared by the citrate-mediated reduction of HAuCl4. A stirred aqueous solution of HAuCl4 (0.29 mM, 50 mL) was heated to reflux, and then a trisodium citrate solution (38.8 mM, 5 mL) was added quickly. Then, the solution was heated under reflux for an additional 10 min and then cooled to room temperature. The as-prepared AuNP solution (20 mL) was mixed with a THF solution of cyclooctyne disulfide 2 (10 μM, 4 mL) and an aqueous solution of thiol-PEG (10 μM, 4 mL), and the resulting mixture was stirred at 40 °C for 2 h. Subsequently, an aqueous solution of 1 (10 μM, 4 mL) was added, stirring at 40 °C for another 4 h. The resulting mixture was centrifuged at 8000 rpm for 17 min and the residual solid product redispersed in Tris-HCl buffer solution (20 mL). This process was repeated three times to remove excessive reactants.The as-obtained glyco-AuNPs (dissolved in Tris-HCl buffer containing 10 nM BSA) were used directly for aggregation with lectins.