Comparative study of microcapsules elaborated with three polycations (PLL, PDL, PLO) for cell immobilization

Alginate-poly-L-lysine (PLL)-alginate microcapsules have been widely used in cell microencapsulation technology. However, the mechanical fragility and low tensile resistance against swelling of this membrane chemistry and the difficult handling, immunogenicity and cytotoxicity of PLL have stimulated the study of novel polycations. In this paper, alginate microcapsules coated with three different polycations: poly-L-lysine (PLL), poly-D-lysine (PDL) and poly-L-ornithine (PLO) were fabricated to evaluate if the use of novel membrane chemistries (PDL, PLO) had a positive effect on the morphology, osmotic resistance and mechanical stability of the capsules as well as the viability of the immobilized C2C12 myoblast cells when compared to the classical PLL microcapsules. Results indicate that liquefied capsules presented worse mechanical properties than the polymerized solid capsules in the three type of membrane chemistries. In addition, PLL membrane chemistry exerted the highest resistance against compressions after culture in several mediums, while PDL microcapsules showed the highest resistance to the tensile stress of the osmotic pressure. No important differences were detected when the physiological activity of the enclosed cells was evaluated. In summary, although further in vivo assays are needed, in general none of the new membrane formulations represented a significant improvement over classical PLL microcapsules.