Fabrication of Hybrid Capsules via CaCO 3 Crystallization on Degradable Coacervate Droplets.

Organic-inorganic CaCO3 capsules were prepared by crystallization of CaCO3 on Pickering emulsion prepared using coacervate droplets made from thermoresponsive and degradable poly(2-methylene-1,3-dioxepane- co-2-hydroxyethyl acrylate) (poly(MDO- co-HEA)) in sole aqueous medium. The diameters of CaCO3 -based Pickering emulsion could be controlled by varying several parameters: diameter of CaCO3 powders, initial polymer concentration, and copolymer composition. The CaCO3 Pickering emulsion was able to load low-molecular-weight hydrophobic substances at temperatures above the lower critical solution temperature (LCST) due to formation of polymer-concentrated phases, i.e., coacervate droplets. The diameter of CaCO3 capsules prepared by crystallization also depended on the diameter of the CaCO3 Pickering emulsion. The CaCO3 shell was composed of calcite-type crystals, the most stable polymorph among known CaCO3 crystals. The facially prepared CaCO3 capsules are valuable for use in functional biomaterials, such as drug delivery carriers and cell culture scaffolds for noninvasive bone-regenerative medicine.