Preparation of Alginate Hydrogel Beads on a Superhydrophobic Surface with Calcium Salt Powder to Enhance the Mechanical Strength and Encapsulation Efficiency of Ingredients

Calcium alginate hydrogel is one of the most widely used materials for drug-carrier beads used in drug-delivery systems. In this study, we developed a new method to improve the encapsulation efficiency of ingredients, such as medicines, in calcium alginate hydrogel beads. In the gold standard method, the hydrogel beads are prepared in the liquid phase. In contrast, in the new method, to enhance the encapsulation efficiency, the hydrogel beads are prepared in the gas phase using a water-repellent surface. In brief, a droplet of sodium alginate aqueous solution is rolled on a water-repellent surface with CaCl2 powder, a cross-linking agent. This process leads to the direct attachment of CaCl2 powder to the droplet, resulting in the formation of spherical hydrogel beads with high mechanical strength and higher encapsulation efficiency than beads prepared by previous methods. The hydrogel beads exhibit similar permeability for glucose, a model for low-molecular-weight medicines, to those prepared by previous methods. These results show that the new method is promising for the preparation of calcium alginate hydrogel beads for drug-delivery systems.