Abstract
We have been developing optical nanoprobes based on lectin-conjugated gold nanoparticles that selectively and sensitively detect a multifunctional glycoprotein “lactoferrin” through glycan–lectin interactions. Nanoparticle aggregations induced by specific glycan–lectin interactions shift the plasmon absorption to longer wavelength and increase the plasmon light scattering. The dissociation constants (Kd) for glycan–lectin interactions were calculated from light-scattering spectral data by performing computer simulations. The obtained Kd values were considerably lower than those of monosaccharaides, indicating higher affinity for lactoferrin glycans. These results reveal that the presence of multiple carbohydrate ligands on gold nanoparticle surfaces significantly enhances the affinity for lectins relative to that for monosaccharaides. Lactoferrins can be detected with a high sensitivity using such lectin-conjugated gold nanoparticles. In particular, gold nanoparticles covalently conjugated to Concanavaline A (Con A) have a better sensing performance than those electrostatically conjugated to Con A dose. The light-scattering intensities are proportional to the lactoferrin concentration in the range of 509.0–9.0 nM. The limit of detection and the sensitivity are 5.6 nM and 0.5 nM–1, respectively. The sensitivity can be tuned by changing the amount of lectins immobilized on gold nanoparticles.
