Fabrication of highly stable glyco-gold nanoparticles and development of a glyco-gold nanoparticle-based oriented immobilized antibody microarray for lectin (GOAL) assay.

The design of high-affinity lectin ligands is critical for enhancing the inherently weak binding affinities of monomeric carbohydrates to their binding proteins. Glyco-gold nanoparticles (glyco-AuNPs) are promising multivalent glycan displays that can confer significantly improved functional affinity of glyco-AuNPs to proteins. Here, AuNPs are functionalized with several different carbohydrates to profile lectin affinities. We demonstrate that AuNPs functionalized with mixed thiolated ligands comprising glycan (70 mol %) and an amphiphilic linker (30 mol %) provide long-term stability in solutions containing high concentrations of salts and proteins, with no evidence of nonspecific protein adsorption. These highly stable glyco-AuNPs enable the detection of model plant lectins such as Concanavalin A, wheat germ agglutinin, and Ricinus communis Agglutinin 120, at subnanomolar and low picomolar levels through UV/Vis spectrophotometry and dynamic light scattering, respectively. Moreover, we develop in situ glyco-AuNPs-based agglutination on an oriented immobilized antibody microarray, which permits highly sensitive lectin sensing with the naked eye. In addition, this microarray is capable of detecting lectins presented individually, in other environmental settings, or in a mixture of samples. These results indicate that glyconanoparticles represent a versatile and highly sensitive method for detecting and probing the binding of glycan to proteins, with significant implications for the construction of a variety of platforms for the development of glyconanoparticle-based biosensors.

Multivalent glycosylated nanoparticles for studying carbohydrate-protein interactions.

Carbohydrates are essential mediators of many important extracellular binding events. Multivalent effects are often required for these binding interactions that are generally weak. Biologically significant carbohydrate-modified nanomaterials are an appealing model system for a systematic investigation of multivalent binding effects. This review seeks to highlight recent striking examples of multivalent glycosylated nanomaterials concentrating on carbohydrate-protein interactions. The specific aim is to provide an overview of various aspects of glyco-nanoparticles in binding assays, targeted therapy, molecular imaging, enzyme activity assay, and bacterium detection.

Total synthesis of an immunomodulatory phosphoglycolipid from thermophilic bacteria.

A method for the stereocontrolled synthesis of a bacterial phosphoglycolipid (PGL1) isolated from thermophilic bacteria is described. The key features of the synthesis include a highly α-selective glycosylation reaction between a trichloroacetimidate donor and a D-lyxose-derived primary alcohol acceptor and the late-stage incorporation of the phospholipid.

Synthesis of serine-based glycolipids as potential TLR4 activators.

A new series of monosaccharide-based glycolipids devoid of phosphate groups and with two lipid chains were rationally designed by varying the lipid chain lengths and saccharide structure of a α-GalCer-derived lead compound (CCL-34) that is a potent TLR4 agonist. The NF-κB activity of a 60-membered galactosyl serine-based synthetic library containing compounds with various lipid chain lengths was measured in a HEK293 cell line that stably expressed human TLR4, MD2, and CD14 (293-hTLR4/MD2-CD14). The results showed that the optimal carbon chain lengths for the lipid amine and fatty acid to activate TLR4 were 10-11 and 12, respectively. Evaluation of a 20-membered synthetic glycosyl serine-based lipid library containing compounds with various saccharide moieties and fixed lipid chain lengths revealed that the galactose moiety in CCL-34 could be replaced by glucose without loss of activity (CCL-34-S3 and CCL-34-S16). Changing the orientation of the anomeric glycosidic bond of CCL-34 resulted in a complete loss of activity (ß-CCL34). Surprisingly, a change in configuration of the anomeric glycosidic bond in a glucosyl glycolipid is tolerable (CCL-34-S14). Another noteworthy observation is that the activity of a l-fucosyl derived glycolipid (CCL-34-S13) was comparable to that of CCL-34. In sum, this study determines the structural features that are crucial for an optimal TLR4-stimulating activity. It also provides several molecules with immunostimulating potential.