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 mono -disperse 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.