Internal gelation of alginate microparticle prepared by emulsification and microfluidic method: Effect of Ca-EDTA as a calcium source

Alginate microparticles were prepared by emulsification/internal gelation and microfluidic/internal gelation technique. Calcium-ethylenediaminetetraacetic acid (Ca-EDTA) was used as a calcium source, which could release Ca2+ ions to crosslink with the alginate chain by adding acid. Effects of emulsification speed, Ca-EDTA concentration, and crosslinking time on morphology, mechanical properties, rheological properties were investigated. A high-speed homogenizer was used to reduce the W/O emulsion size in the emulsification method. The smooth surface morphology of alginate particles was found from internal gelation while particles from external gelation showed a rough surface. Mechanical and rheological measurements demonstrated that a higher Ca2+ provided denser particles. The crosslinking time played a significant role in rheological properties. Double-gelation which was internal gelation followed by external gelation resulted in even higher stiffness compared with the particles from only internal crosslinking. Using the microfluidics technique, we could generate monodisperse alginate particles with more uniformity and controllable size. Thus, alginate particles can be fabricated using a continuous process which can avoid batch-to-batch variation.