Scheme 1.

A schematic illustration of the procedure for preparing ACA microcapsules with a liquid core loaded with cells by 1, electrospraying to produce cell loaded plain alginate microbeads (a solid microsphere of alginate hydrogel with no shell); 2, coating the microbeads with chitosan to form aliginate-chitosan (AC) microcapsules (with an AC shell); 3, coating the AC microcapsules further with alginate to form alginate-chitosan-alginate (ACA) microcapsules (with an ACA shell and solid-like core of alginate hydrogel loaded with cells); and 4, liquefying the alginate hydrogel core to give rise to the ACA microcapsules with a liquid core loaded with cells: The letters G and M represent the guluronate and mannuronate blocks in alginate, respectively.