Development and optimisation of alginate-PMCG-alginate microcapsules for cell immobilisation

Mechanical stability, uniformity of size, complete encapsulation of cells and optimal microenvironment are major challenges in the design and development of microcapsules for cell immobilisation purposes. In this work, a novel microcapsule chemistry based on polyelectrolyte complexation between alginate and poly(methylene-co-guanidine) (PMCG) is presented. We have characterised the effect of PMCG concentration and time of exposure on microcapsule diameter and membrane thickness, selecting a PMCG concentration of 0.5% (v/v) and an exposure time of 1 min as optimal parameters for a correct coating. Afterwards, the mechanically most resistant alginate-PMCG-alginate (A-PMCG-A) microcapsule type was chosen according to two different stability studies. Beads with a solid core and an inhomogeneous internal configuration resulted in stronger microcapsules. Further, the selected A-PMCG-A beads presented both an increased stability compared to classical Ca(2+)/alginate and alginate-poly-L-lysine-alginate (APA) microcapsules, and had an adequate microenvironment for cell viability. This new chemistry allows the controlled adjustment of microcapsule size and wall thickness, offering new alternatives for cell transplantation.