Uniform chitosan-coated alginate particles as emulsifiers for preparation of stable Pickering emulsions with stimulus dependence

Owing to the absence of surfactants, Pickering emulsion shows little toxicity and emerges as an alternative for preparing potential carriers in biomedical area. Alginate particles are attractive stabilizers for this emulsion owing to their biocompatibility and pH sensitivity. However, their performance is still dissatisfactory due to the difficulty in preparing uniform submicron particles and the inappropriate hydrophilic property. In this study, we developed two strategies to circumvent above shortcomings. Uniform alginate particles with submicron to micron size were successfully prepared by premix membrane emulsification. In addition, the uniform particles were coated with relatively hydrophobic chitosan to overcome the high hydrophilicity of alginate particles. These uniform coated particles effectively stabilized the oil-in-water Pickering emulsion. It was found that the stability of emulsions was tremendously affected by particle size, and the least particle concentrations required for emulsion stability were proportional to the particle radii. Besides the particle size, the pH and salt concentration of aqueous phase was demonstrated to impact the stability of emulsions. The underlying mechanism was discussed in detail, concerning with three different-sized particles. Present work provided an effective strategy to prepare Pickering emulsion, which can be applied to design potent carriers in biomedical area.