Fabrication of Ca-alginate microspheres by diffusion-induced gelation in double emulsion droplets for oral insulin

Sodium alginate has good biocompatibility and is widely used in the study of drug carriers. In this paper, a method to prepare calcium alginate microspheres with high sphericity based on double emulsion droplets was proposed, in which sodium alginate is used as the innermost phase. By adjusting the density of the system, the double-emulsion droplets could be suspended in the collecting solution, leading to the homogeneous reaction between the sodium alginate droplets and the calcium ions. By changing the flow rate, the size of the droplets could be changed, and by changing the concentration of calcium ions in the collecting solution, the sphericity of the calcium alginate microspheres could be changed. Then the swelling properties and drug release properties of calcium alginate microspheres were determined. The drug delivery study revealed that the insulin-loaded Ca-Alginate microspheres were able to decrease blood glucose by 41.4 % after oral administration to mice. Thus, the Ca-Alginate microsphere is a suitable candidate for controlled pH-sensitive drug delivery.