Water-in-water(W/W) emulsions, composed entirely of immiscible aqueous phases without organic solvents, offer excellent biocompatibility and eco-friendliness. However, their low interfacial tension leads to rapid desorption of stabilizers, resulting in poor W/W emulsion stability. This instability causes premature payload release and complicates long-term storage.
To address this, we enhanced W/W emulsion stability by using colloidal particles surface-modified with a hydrophilic polymer. These modified particles were densely adsorbed at the water-water interface, successfully stabilizing the W/W emulsion for three months without any changes in droplet size. Furthermore, droplet size was precisely controlled by adjusting particle size and interfacial tension. This stabilized W/W emulsion provides a versatile platform for designing stable water-based drug delivery systems with controlled release.