Antimicrobial Microcapsule for Encapsulation and Sustained Release of Grapefruit Essential Oil (GEO)

In this study, grapefruit essential oil (GEO)-loaded microcapsules encapsulated within silver/calcium alginate (Ag/CA) composite shells were successfully fabricated through an electrostatic spray technique. First, a pre-emulsion of GEO was prepared in the presence of sodium dodecyl sulfate (SDS) and sodium alginate (SA). Subsequently, the pre-emulsion was sprayed into an aqueous calcium chloride solution using electrostatic spray technique in the form of microdroplets, yielding calcium alginate (CA) gel microcapsules encapsulating GEO. Then, the previously prepared CA@GEO microcapsules were introduced into hydroxymethyl aminomethane (Tris) buffer solution, followed by the addition of dopamine hydrochloride. This enabled dopamine adsorption onto the microcapsule surface and subsequent polymerization to form a polydopamine layer. Finally, the dopamine hydrochloride-treated CA@GEO microcapsules were placed into a silver ammonia solution, where coordination interaction occurred between the polydopamine (PDA) on the microcapsule surface and silver ammonia particles. Subsequent in situ reduction, facilitated by glucose acting as a reducing agent, resulted in the formation of a silver shell on the microcapsule surface. The morphology and structure of the microcapsules were comprehensively characterized using scanning electron microscopy (SEM), particle size distribution analysis, x-ray photoelectron spectroscopy (XPS), etc. Moreover, the sustained release and antibacterial properties of Ag/CA@GEO microcapsules were investigated. Graphical A pre-emulsion of grapefruit essential oil (GEO) was prepared with sodium dodecyl sulfate and sodium alginate as stabilizers. Calcium alginate (CA) gel microcapsules encapsulating GEO were prepared by electrostatically spraying the pre-emulsion as microdroplets into an aqueous calcium chloride solution. Subsequently, a polydopamine layer was deposited onto the microsphere surfaces; this layer chelated silver ammonia ions and facilitated in-situ reduction in the presence of glucose, ultimately yielding a dense silver shell on the microspheres.