Microfluidic approach to produce emulsion-filled alginate microgels

Carrying lipophilic compounds protection within alginate microgels is a challenge, mainly due to the necessary oil-core matrix. Based on this demand, this study aimed to evaluate the use of glass microfluidic devices to produce emulsion-filled alginate microgels and understand the effect of process variables on microgels size and polydispersity. Firstly, stable and monodisperse size-distributed oil microdroplets were formed by preparing an oil-in-water (O/W) emulsion using high shear followed by ultrasound. The continuous aqueous phase was composed of Na-alginate, cellulose nanocrystals and ultrafine calcium carbonate. Sunflower oil composed the emulsion oil phase (10%, w/w). Secondly, oil-in-water-in-oil (O/W/O) emulsions were formed within microfluidics devices to obtain emulsion-filled hydrogel particles. The previously produced O/W emulsion was introduced as the dispersed phase into a continuous phase containing sunflower oil, PGPR and acetic acid. The aqueous phase was gelled by internal gelation, promoting the alginate network. Monodisperse particle size distribution was observed, with a coefficient of variation lower than 6% and mean size ranging from 259 to 526 μm. Microgels size was influenced by the viscosity of O/W emulsion and the phases flow rates. Our results show the potential of microfluidic processes for producing microgels and filled microgels to encapsulate lipophilic compounds.