Development of alginate–agarose subsieve-size capsules for subsequent modification with a polyelectrolyte complex membrane

Immunoisolatability, mechanical stability and biocompatibility of cell-enclosing microcapsules are controlled by the formation of external polyelectrolyte complex membranes. The present study aimed to develop cell-enclosing subsieve-size capsules of less than 100 μm in diameter for controlling these properties. We investigated the use of anionic polysaccharide alginate combined with thermosensitive agarose, and prepared particles composed of the two components. For this purpose, agarose in droplets suspended in liquid paraffin was first gelated by cooling, and followed by gelation of alginate in CaCl2 solution. Treatment with a solution containing cationic polysaccharide chitosan inhibited the diffusion of bovine serum albumin into particles compared with non-treated particles. This observation showed that alginate–agarose particles were successfully coated with the polyelectrolyte complex membrane. In addition, cells enclosed in subsieve-size alginate–agarose capsules prepared via the gelation process adapted to the microenvironment and showed mitochondrial activity during 27 days of study. These results showed that alginate–agarose capsules prepared via the droplet breakup method in a water-immiscible co-flowing fluid and the subsequent ordered gelation process were effective vehicles for cell-encapsulation devices for cell therapy.