Pickering particles as interfacial reservoirs of antioxidants

Emulsions are common structures encapsulating lipophilic bioactive molecules, both in biological systems and in manufactured products. Protecting these functional molecules from oxidation is essential; Nature excels at doing so by placing antioxidants at the oil-water interface, where oxidative reactions primarily occur. We imagined a novel approach to boost the activity of antioxidants in designer emulsions by employing Pickering particles that act both as physical emulsion stabilizers and as interfacial reservoirs of antioxidants.

α-Tocopherol or carnosic acid, two model lipophilic antioxidants, were entrapped in colloidal lipid particles (CLPs) that were next used to physically stabilize sunflower oil-in-water emulsions ("concept" Pickering emulsions). We first assessed the physical properties and stability of the CLPs and of the Pickering emulsions. We then monitored the oxidative stability of the concept emulsions upon incubation, and compared it to that of control emulsions of similar structure, yet with the antioxidant present in the oil droplet interior.

Both tested antioxidants are largely more effective when loaded within Pickering particles than when solubilized in the oil droplet interior, thus confirming the importance of the interfacial localization of antioxidants. This approach revisits the paradigm for lipid oxidation prevention in emulsions and offers potential for many applications.