Improving covalent cell encapsulation with temporarily reactive polyelectrolytes

Calcium alginate/poly-l-lysine beads were coated with either 50% hydrolyzed poly(methyl vinyl ether–alt–maleic anhydride) (PMM50), or with poly(vinyl dimethyl azlactone-co-methacrylic acid) (50:50, PMV50), to form covalently shell-crosslinked capsules, and compared with analogous capsules coated with sodium alginate. All capsule types were prepared with and without C2C12 murine myoblast cells, and implanted into mice for up to 6 weeks. Cell viability, capsule integrity, fibrotic overgrowth, and mechanical strength of the capsules were assessed, and correlated with inflammatory cytokine marker levels in tail vein blood samples taken at different time points. AP-PMM50 capsules displayed the least amount of fibrotic overgrowth, were found to be the strongest, and showed the lowest levels of TNF-α in tail vein serum samples taken at 4 h, 24 h, 1 and 6 weeks post transplantation. The results for APA and AP-PMV50 capsules were more variable and depended on the presence or absence of encapsulated cells.