Thermodynamic Evidence for Ca2+-Mediated Self-Aggregation of Lewis X Gold Glyconanoparticles. A Model for Cell Adhesion via Carbohydrate−Carbohydrate Interaction

Abstract
Thermodynamic evidence for the selective Ca2+-mediated self-aggregation via carbohydrate−carbohydrate interactions of gold glyconanoparticles functionalized with the disaccharides lactose (lacto-Au) and maltose (malto-Au), or the biologically relevant trisaccharide Lewis X (LeX−Au), was obtained by isothermal titration calorimetry. The aggregation process was also directly visualized by atomic force microscopy. It was shown in the case of the trisaccharide Lewis X that the Ca2+-mediated aggregation is a slow process that takes place with a decrease in enthalpy of 160 ± 30 kcal mol-1, while the heat evolved in the case of lactose and maltose glyconanoparticles was very low and thermal equilibrium was quickly achieved. Measurements in the presence of Mg2+ and Na+ cations confirm the selectivity for Ca2+ of LeX−Au glyconanoparticles. The relevance of this result to cell−cell adhesion process mediated by carbohydrate−carbohydrate interactions is discussed.