Controllable fabrication of core-shell microcapsules using sodium alginate/gellan gum as shell material by microfluidics

Abstract

Core-shell microcapsules are of considerable importance in the food and pharmaceutical industries, due to their ability to encapsulate functional ingredients. The hydrophilic sodium alginate/gellan gum (SA/GG) crosslinked with Ca²⁺ shows great application potential using as the shell materials of microcapsules encapsulating hydrophobic components. However, its adaptability using as shell materials of microcapsules for double emulsion template method has rarely been evaluated. Here, it was controlled fabricated by microfluidics through a double emulsion template method using sodium alginate/gellan gum (SA/GG) as shell material. Inclusion of Ca²⁺ enhanced intermolecular interactions in shell material of SA/GG, especially with a component ratio of 4:6, by conjoining the “egg-box” structure of SA and Ca²⁺-mediated GG networks to greater extent and increased its gel strength. This favors the fabrication of core-shell microcapsules with desired size, morphology, and mechanical strength. Increasing SA content decreased the minimum Q₀ (flow rate of outer phase) values and increased the maximum Q_m (flow rate of middle phase) for the emulsion generation, simultaneously, due to the reduced molecular entanglements and the solution viscosity. These findings provide a strategy for controllable preparation of monodispersed microcapsules encapsulating oily substances or oil-soluble bioactive substances by microfluidics.