Enhancing oxygen tension and cellular function in alginate cell encapsulation devices through the use of perfluorocarbons

Abstract

Encapsulation devices are often hindered by the inability to achieve sufficient oxygen levels for sustaining long-term cell survival both in vivo and in vitro. We have investigated the use of synthetic oxygen carriers in alginate gels to improve metabolic activity and viability of HepG2 cells over time. Perfluorocarbons (PFCs), specifically perfluorotributylamine (PFTBA) and perfluorooctylbromide (PFOB), were emulsified with alginate and used to encapsulate HepG2 cells in a spherical geometry. Cellular state was assessed using the MTT assay and Live/Dead stain as well as through analysis of both lactate and lactate dehydrogenase (LDH) levels which are indirect indicators of oxygen availability. Addition of 1% surfactant resulted in stable emulsions with evenly dispersed PFC droplets of the order of 1-2 microm in diameter, with no influence on cell viability. Both PFCs evaluated were effective in increasing cellular metabolic activity over alginate-only gels. The presence of 10% PFOB significantly increased cellular growth rate by 10% and reduced both intracellular LDH and extracellular lactate levels by 20-40%, improving glucose utilization efficiency. The characteristic drop in cellular metabolic activity upon encapsulation was eliminated with addition of 10% PFC and viability was better maintained throughout the bead, with a significant decrease in necrotic core size. Results were consistent under a physiologically relevant 5% oxygen environment. The incorporation of PFC synthetic oxygen carriers into encapsulation matrices has been successfully applied to improve cell function and viability with implication for a variety of tissue engineering applications.