Encapsulation of Proteins into CaCO₃ by Phase Transition from Vaterite to Calcite

Abstract

Phase transition from vaterite to calcite is a general behavior of CaCO3 materials. The interfacial reaction method using water-in-oil-in-water (W/O/W) emulsion we reported before is an effective method to produce hollow CaCO3 particles (microcapsules) with vaterite crystalline structure. These vaterite CaCO3 microcapsules underwent the phase transition to calcite in various aqueous solutions. When some proteins were mixed in the solution used for the phase transition, their encapsulations were achieved satisfactorily at room temperature regardless of their molecular weight. Insulin, lysozyme, bovine serum albumin, and chicken IgY were successfully encapsulated into the phase transition CaCO3 particles, while the encapsulation of lysozyme was unsuccessful by the interfacial reaction method. Protein included in the phase transition CaCO3 particle was not discharged by simple water washing but by the dissolution of the CaCO3 matrix in an acid solution, being advantageous to a responsive protein delivery technology. The recycle uses of the insulin solution used for the encapsulation improved the utilization efficiency of insulin. It was ascertained that the phase transition of vaterite CaCO3 microcapsule to calcite is a simple, general, and convenient method to encapsulate proteins into CaCO3 small particles under very mild conditions.

Release of Insulin from Calcium Carbonate Microspheres with and without Layer-by-Layer Thin Coatings

“…It is clear that the phase transition in the crystal form of CaCO 3 occurred during the insulin release in the buffer solution as a result of the simultaneous partial dissolution of CaCO 3 microspheres and precipitation of calcite crystals. A similar phase transition in CaCO 3 microspheres has recently been reported [24]. The crystalline phase of CaCO 3 readily changes from metastable vaterite to stable calcite in solution [26,27].…”

“…Figure 2 shows SEM images of insulin-containing CaCO 3 microspheres before and after the microspheres were immersed in the buffer solution at pH 7.4. The as-prepared CaCO 3 microspheres were spherical with a rough surface, which is typical for vaterite morphology [24]. However, after soaking the CaCO 3 microspheres in the buffer solution, the microspheres changed to rhombohedral crystals characteristic of calcite [25].…”

Microencapsulation of phase change materials with binary cores and calcium carbonate shell for thermal energy storage

“…It is well known that CaCO 3 has three crystalline polymorphs, i.e., calcite, aragonite, and vaterite, which correspond to different morphologies and fit for different application fields [35]. Moreover, CaCO 3 crystal can be mutual transformed through additive varieties and surfactant concentration [36]. It is noteworthy that the bowl-like shell is uncommon in the crystal forms of CaCO 3 .…”

Diatom-inspired skeletonisation of insulin – Mechanistic insights into crystallisation and extracellular bioactivity

“…Calcium carbonate has been long considered an effective matrix for delivery systems [23,24,25,26], having been loaded as microcapsules, with biomacromolecules such as insulin and bovine serum albumin (BSA) [27]. Direct encapsulation of biomacromolecules into calcium carbonate particles by either interfacial reaction using n-hexane solution [44] or through simple mixing [45] is also proven to be highly efficient and comparable to similar methods using silica microcapsules [44].…”