Quantitative Analysis of Multivalent Ligand Presentation on Gold Glyconanoparticles and the Impact on Lectin Binding

Abstract

Glyconanomaterials, nanomaterials carrying multiple carbohydrate ligands, provide an excellent platform for sensitive protein recognition. Using nanomaterials as the scaffold, multivalent interactions between glycan ligands and proteins have been demonstrated. However, the quantitative analysis of the binding affinity of these glyconanomaterials has been lacking. In this article, we report a new method to measure the binding affinity of glyconanoparticle (GNP)-protein interactions based on a fluorescent competition binding assay, which yielded the apparent dissociation constant (Kd) of GNPs with the interacting protein. Au nanoparticles conjugated with underivatized mono-, oligo-, poly-saccharides were synthesized using our recently developed photocoupling chemistry. The affinities of these GNPs with lectins were measured and were several orders of magnitude higher than the corresponding free ligands with lectins. The effect of ligand display on the binding affinity of GNPs was furthermore studied where GNPs of varying linker type, spacer length, ligand density, and nanoparticle size were prepared and Kd values determined. The long spacer linker containing hydrocarbon and ethylene oxide units gave the highest binding affinity as well as assay sensitivity. The binding affinity increased with ligand density in general, showing a drastic increase in affinity at low ligand density. In addition, the affinity enhancement was more pronounced on smaller NPs than the larger ones. These results not only demonstrate that the binding affinity of GNPs is highly influenced by how the ligands are presented on the nanoparticles, but also pave the way for tailor-made glyconanomaterials with tunable affinity by way of ligand display.

Glyconanoparticles for colorimetric bioassays

“…81 a) b) Wang et al found that the sensitivity of mannose-functionalised nanoparticles towards ConA increased with the spacer length. 82 The authors prepared the glyconanoparticles using a photocoupling method, as previously described in this review, 66 and more flexible spacer linkage exhibited the lowest limit of detection. 82 While these results appear to contradict previous work, 52,76,78 it is possible that the flexibility of the anchor chain is an additional important feature for the targeting and sensitive detection of proteins with glyconanoparticles.…”

Fabrication of Highly Stable Glyco‐Gold Nanoparticles and Development of a Glyco‐Gold Nanoparticle‐Based Oriented Immobilized Antibody Microarray for Lectin (GOAL) Assay

“…[35] Therefore, the lectin can act as a crosslinker. Antibodies on the surface captured the A chain(s) of RCA 120 , and the remaining two Lac-binding B chains and RCA 120 in solution aggregated simultaneously GOAL assay [c] 5-AuNP 6-AuNP 7-AuNP RCA 120 Con A WGA 300 (7 nm) [17] 430 (6.2 nm) [23] 500 (1.5 nm) [45] 3 (6.6 nm) [24] 16 (15 nm) [24] 12…”

Gold Nanoparticles in Biosensing Analyses

“…Due to the high dielectric constant of AuNPs and electromagnetic coupling between AuNPs and the metal film on the surface, the sensitivity of the surface plasmon resonance (SPR)-based sensor can be increased. Several different materials are also used to support AuNPs such as optical fibres, ITO glass, sol-gel matrix for the detection of human IgG [50], streptavidin [51], interleukin-1β [52] and propanethiol [53]. Similarly, waveguide-mode sensor, which mimic the principle of SPR, has been generated with higher sensitive sensing using AuNP conjugation for the detection of influenza viruses [10][11][12].…”