Preparation and characterization of gliadin-based core-shell microcapsules by three antisolvent approaches

Gliadin, a versatile wheat-derived protein, has great potential in the creation of nanostructured delivery systems for encapsulating various hydrophobic bioactive substances. Despite gliadin's well-established potential in creating nanostructured delivery systems for hydrophobic substances, its utilization for encapsulating hydrophilic compounds remains a relatively unexplored domain. This study investigated the feasibility of preparing gliadin-based core-shell microcapsules using different antisolvent methods and assessed their controlled release capabilities for hydrophilic compounds. It employed three commonly used food polysaccharides, alginate, κ-carrageenan, and agar, as hydrophilic microbeads and selected thiamine and ethyl maltol as model compounds. The microcapsules were constructed by two steps: 1) The microbeads were prepared by a water-in-oil emulsion template under different gelling conditions; 2) The microbeads were dispersed into aqueous ethanol/urea/acetic acid gliadin solutions, during which the slow migration of water from inside the microbeads to the outer gliadin solution decreased the solubility of gliadin and promoted the deposition of gliadin onto the surface of the microbeads, finally leading to the formation of the core-shell structure. The resulting core-shell microcapsules exhibited adjustable particle sizes from 80.0-850.0 μm in diameter and shell thickness ranging from 8.0-30.0 μm. Moreover, the microcapsules exhibited controlled release behavior for hydrophilic compounds, with only 20.0% of thiamine being released after 90 min, and this release rate can be finely tuned by controlling the shell thickness. These gliadin-based core-shell microcapsules are considered as promising carriers for the controlled delivery of hydrophilic compounds.