Novel Water-in-Water Emulsions: Formation, Stabilization and Possible Applications as Drug Delivery Systems

Water-in-water (W/W) emulsions are colloidal dispersions formed in aqueous two-phase systems, because of thermodynamic incompatibility between two hydrophilic macromolecules in aqueous solution, in absence of surfactant and without oil [1]. W/W emulsions can be can be prepared in mixtures of edible macromolecules, such as proteins and polysaccharides (Fig. 1). These fat-free emulsions can be highly interesting for formulation of functional food products and oral delivery of active components.

We have obtained W/W emulsions in aqueous mixtures of gelatin and carboxymethyl cellulose and these emulsions could entrap probiotic bacteria [2]. In another work, we used gelatin-in-maltodextrin W/W emulsions for the encapsulation of lactase inside gelatin microgels cross-linked with genipin. The enzyme showed a high degree of activity and gelatin microgels provided protection in a simulated gastric fluid [3]. More recently, we obtained multiple water-in-water-in-water emulsions by a simple method that consisted in cooling down gelatin-in-maltodextrin (G/M) emulsions, leading to the spontaneous formation of inner maltodextrin droplets and producing M/G/M multiple droplets [4]. The colloidal stability of M/G/M emulsions was much increased by the adsorption of mucin particles at the G/M interface.

Fig. 1. Fluorescence optical microscopy images of W/W emulsions. (a) Dextran-in-in gelatin emulsions; (b) Gelatin-in-maltodextrin emulsions, with mucin particles at the interface.

References

[1] J. Esquena, Current Opinion in Colloid and Interface Science, 25 (2016) 109

[2] Singh P., Medronho B., Miguel M.G., Esquena J., On the encapsulation and viability of probiotic bacteria in edible carboxymethyl cellulose-gelatin water-in-water emulsions, (2018) Food Hydrocolloids, 75, pp. 41 – 50

[3] Beldengrün Y., Aragon J., Prazeres S.F., Montalvo G., Miras J., Esquena J., Gelatin/Maltodextrin Water-in-Water (W/W) Emulsions for the Preparation of Cross-Linked Enzyme-Loaded Microgels, (2018) Langmuir, 34 (33), pp. 9731 – 9743.

[4] Beldengrün Y., Dallaris V., Jaén C., Protat R., Miras J., Calvo M., García-Celma M.J., Esquena J., Formation and stabilization of multiple water-in-water-in-water (W/W/W) emulsions, (2020) Food Hydrocolloids, 102, art. no. 105588.