Abstract
The major challenge in developing cryopreservation protocols for microencapsulated cells is that the relatively large size (300–400 μm) and the fragile semipermeable membrane of microcapsules makes them particularly prone to cryodamage. Rapid‐cooling cryopreservation protocols with high DMSO concentrations (3.5M, 25% v/v) resulted in low post‐thaw cell viability (<10%), which did not improve with higher concentrations (4.5M, 32% v/v) and longer exposure to DMSO, even though the majority of microcapsules (60–80%) remained intact. Subsequent investigations of slow cooling with a range of DMSO and EG concentrations resulted in a much higher post‐thaw cell viability (80–85%), with the majority of the microcapsules remaining intact (∼60%) when DMSO was used at a concentration of 2.8M (20% v/v) and EG at a concentration of 2.7M (15% v/v). The presence of 0.25M sucrose significantly improved post‐thaw cell viability upon slow cooling with 2.8M (20% v/v) DMSO, although it had no effect on microcapsule integrity. Multistep exposure and removal of sucrose did not significantly improve either post‐thaw cell viability or microcapsule integrity, compared to a single‐step protocol. Ficoll 20% (w/v) also did not significantly improve post‐thaw cell viability and microcapsule integrity. Hence, the optimal condition for microcapsule cryopreservation developed in this study is slow cooling with 2.8M (20% v/v) DMSO and 0.25M sucrose. © 2003 Wiley Periodicals, Inc.