Aggregation behavior of sodium alginate with cucurbit[6]uril in aqueous solution

The interaction between the polysaccharide alginate and cucurbit[6]uril (CB[6]) in aqueous solution has been investigated by static fluorescence spectroscopy, dynamic light scattering, transmission electron microscopy, circular dichroism (CD) and zeta potential. Results showed that the interactions between the alginate and the CB[6] lead to the formation of micelle-like nanometer-sized aggregates due to electrostatic interaction and iondipole interaction. The size of aggregates depends on the concentration of alginate. In our experiment, only when the concentration of sodium alginate was 0.05 wt%, were uniform micelle-like aggregates achieved. With the increase in the concentration of alginate, the size of aggregates increased. When the concentration of alginate was above 0.2 wt%, the aggregates became precipitates after 48 h of storage at room temperature. As the concentration of sodium alginate was raised to about 0.5 wt%, gelation appeared. At low concentrations of alginate (around 0.01 wt%), few micelles-like nanometer-sized aggregates were observed. The aggregation also depends on the mole ratio of CB[6]/carboxyl in alginate. Isolated micelle-like aggregates prevailed at low stoichiometric mole ratio of CB[6]/carboxyl in alginate and the clusters were predominant with increasing the mole ratio of CB[6]/carboxyl in alginate due to the decrease of charges at the surface of the micelle-like aggregates.