Thermodynamic evidence for Ca2+-mediated self-aggregation of Lewis X gold glyconanoparticles.: A model for cell adhesion via carbohydrate-carbohydrate interaction

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 (Le(x)-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 Le(x)-Au glyconanoparticles. The relevance of this result to cell-cell adhesion process mediated by carbohydrate-carbohydrate interactions is discussed.