2016 Volume 65 Issue 2 Pages 71-80
We have developed a rapid colorimetric method of glycoanalysis based on lectin-mediated aggregation of gold nanoparticles modified with glycoprotein. Gold nanoparticles (AuNPs) were surface-modified with a model mannose-rich glycoprotein, bovine lactoferrin (bLf), containing glycans that are accessible for lectin binding even after immobilization. In the presence of concanavalin A (Con A), the bLf-modified gold nanoparticles (bLf-AuNPs) spontaneously aggregated due to mannose-Con A interactions. This aggregation induced a significant red shift in the absorption band of the bLf-AuNPs in the visible region, which was detectable even by the naked eye. Dissociation constants (Kd) for the glycan-lectin interactions were calculated based on a computer simulation of UV-vis spectral titration. The Kd values obtained were considerably lower than those of monosaccharides, demonstrating a glycoside cluster effect in the glycan-lectin interactions. This method has advantages over other methods of glycoanalysis, including easy work-up, rapid detection, and the possibility of characterizing glycans attached to proteins through the use of a wide variety of lectins. Furthermore, the lectin-induced aggregation technique may be used for detection not only of glycoprotein glycans but also of unknown lectin-like receptors.
