PH-controllable stability of iron oxide@chitosan nanocomposite-stabilized magnetic Pickering emulsions

Abstract

The pH-responsiveness of iron oxide@chitosan nanocomposite (IOCS)-stabilized Pickering emulsion (PE) (denoted as IOCS-PE) was investigated. Preparation of the IOCS-PE at pH 4.0 has resulted in PE with the smallest size (1.4 ± 0.2 μm) and highest stability against deformation as compared to those prepared at alkaline conditions (pH ≥ 6.3), due to the change in IOCS surface wettability at increasing pH. To further verify the pH-dependent stability, the IOCS-PE at pH 4.0 was subjected to a simple pH variation to pH 1.5 and pH 7.4, respectively. Superior stability was observed for IOCS-PE tuned to pH 1.5 as compared to pH 7.4 over 120 min with or without magnetic field. This difference in stability could be attributed to the reduction in interparticle electrostatic repulsion stemming from the deprotonation of chitosan’s amino group and IONP’s hydroxyl group at pH 7.4. The magnetic responsiveness of the IOCS-PE was also evaluated by subjecting it to an external magnetic field, demonstrating the feasibility of retaining the IOCS-PE in a specific location of interest via magnetic attraction. In conclusion, the stability of IOCS-PE was found to be pH-dependent, and its retention time could be increased by applying an external magnetic field. The outcomes displayed the potential of the IOCS-PE as stimuli-responsive emulsions for food or pharmaceutical applications.