Curcumin-loaded Pickering emulsion stabilized by pH-induced self-aggregated chitosan particles: Effects of degree of deacetylation and molecular weight

Curcumin, a natural polyphenolic compound, has many health benefits: instabilities and poor solubility limit curcumin's industrial applications. The encapsulation of curcumin in Pickering emulsion can enhance its bioavailability. Developing an efficient and simple method for fabricating a natural emulsifier for Pickering emulsion remains a significant challenge. Chitosan has gained attention for its nontoxicity and excellent emulsifying properties. The purpose of this study was to prepare four different types of self-aggregated chitosan particles using a pH-responsive self-assembling method. The aggregated particle properties are tuned by pH, degree of deacetylation (DDA), and molecular weight (MW) through control of surface charge, size (nano, micro, and floc), and contact angle. Pickering emulsions were prepared using different types of aggregated particles. As MW and pH increase and DDA decreases, aggregated particles networked structures formed, resulting in highly elastic gels more resistant to the breakdown of Pickering emulsion at ambient temperature. When ramped up to higher temperatures, the kinetic energy of aggregated particles increases, disrupting hydrogen bonds and potentially changing the systems from fluids to gels. The aggregated particles-based Pickering emulsion was used as the carrier for curcumin encapsulation. MW and DDA regulate drug loading, encapsulation efficiency, and release profile. It found that DDA and MW were responsible for tuning the properties of Pickering emulsion. This research provides a new perspective on selecting suitable chitosan for controlling the release of bioactive compounds in Pickering emulsions, considering factors such as adjustable rheological properties, microstructure, and macrostructure.