All-aqueous emulsions stabilized by derivatized sporopollenin exine capsules

Sporopollenin Exine Capsules (SpECs) were studied as particle stabilizers in all-aqueous emulsions of polyethylene glycol (PEG) and dextran (Dex) (8 % PEG: 6 % Dex). To investigate the role of particle interactions on stabilization mechanisms, SpECs were derivatized to provide positive charges through amidation, and neutral particles via acetylation. Emulsions with non-derivatized SpECs were stable only at pH 6 and 7 when negative charge was high (around -30 mV). Acetylated SpECs with low charge did not stabilize emulsions, while amidated SpECs stabilized the emulsions at all pH values, independent of the charge. Confocal microscopy showed that emulsion stabilization was most likely obtained through two effects: 1) particle adsorption at the interface through a Pickering-like mechanism, and 2) additional electrostatic repulsion between particles in the continuous phase. Overall, this study revealed diverse mechanisms by which SpECs can stabilize all-aqueous emulsions, highlighting their versatility to be used for specific applications.