Nanospheres of alginate prepared through w/o emulsification and internal gelation with nanoparticles of CaCO3

Gelled nanospheres of alginate are prepared through a single step technique involving emulsification and gelation. CaCO3 nanoparticles, together with glucono delta-lactone (GDL), are dispersed in an alginate solution, which is subsequently dispersed in an oil phase and followed by gelation of the alginate spheres. Rheology and pH time dependence are determined during gelation of macroscopic alginate gels. The results are used to optimize CaCO3/alginate mass ratio and GDL/CaCO3 molar ratio in the recipe for formation of the alginate spheres. It is found that nanoparticles of CaCO3 result in smaller alginate spheres and reduces the gelation time significantly, compared to microparticles of CaCO3. Cryo-SEM and light microscopy confirmed the formation of gelled alginate spheres below 10 µm with majority of spheres smaller than 2 µm and even spheres below 200 nm are observed. The extension into the nano range, the reduction in gelation time, and the possibility of a final internal pH around 6 all significantly extend the range of applications for these alginate nanospheres.