Fabrication of uniform alginate-agarose microcapsules loading FeSO4 using water-oil-water-oil multiple emulsions system combined with premix membrane emulsification technique

• This paper was the first report that entrapping FeSO4 into microcapsules via W1/O1/W2/O2 multiple emulsions combined with premix membrane emulsification technique.
• This study creatively employed agarose to improve the mechanical property of microcapsules loading FeSO4, reducing the possibility of being damaged in complex vitro and vivo environment.
• This paper used pH sensitive materials- alginate and agarose to entrap FeSO4, which not only made it possible for Fe2+ to be controlled release, but also shielded the objectionable odor of FeSO4.

In this study, the uniform alginate-agarose microcapsules entrapping FeSO4 were successfully fabricated by premix membrane emulsification technique combined with ionic crosslinking solidification method. It was the first time to employ four phase emulsions system of W1/O1/W2/O2 for encapsulating FeSO4 into alginate-agarose microcapsules. We systematically investigated how the preparation parameters including type of oil phase and emulsifier, concentrations of alginate and agarose and volume ratios between oil and water phase influenced the stability of emulsions, the morphology and size distributions of microcapsules and loading efficiency of FeSO4. We found that the stability of emulsion was improved with the increase of viscosity and density of outer oil phase (O2), the concentration of emulsifier as well as the volume ratio between inner water phase and inner oil phase (W1/O1) within a certain range. Besides, loading capacity of Fe2+ in alginate/agarose microcapsules presented an increase tendency with the decrease of the volume ratio between external water phase (W2) and primary emulsion [W2/(O1/W1) (v/v)], and also decreased with the concentration of W2. Furthermore, Young’s modulus grew significantly with the increase of agarose/alginate (w/w). According to the above investigation, the optimal preparation parameters were obtained, and the microcapsules prepared with these parameters showed spherical and smooth morphology, average size of 2 μm in diameter, narrow size distributions and higher FeSO4 loading efficiency of 13.7 mg/g. The microcapsules could be applied for the human body iron supplement, and the encapsulation could well shield bad taste of FeSO4.

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