The purpose of this study is to clarify whether encapsulated cells have an advantage over suspended cells in cryopreservation. Rat pheochromocytoma (PC12) cells were selected for test biological cell and microencapsulated in alginate-polylysine-alginate membranes. Microencapsulated PC12 cells were frozen with differential scanning calorimetry (DSC) at a cooling rate of 0.5 to 10°C/min, their latent heat was measured among the freezing process over the temperature range 4 to −80°C. Their post-thaw viability were evaluated by dye exclusion assay and dopamine release. As a result, latent heat of encapsulated cells was lower than that of suspended cells at a cooling rate of 0.5 and l°C/min. This is because extra-capsule was frozen and intra-capsule unfrozen, as ice crystals forms in extra-capsule space. Post-thaw viability of microencapsulated PC12 cells was improved at 0.5 and l°C/min compared with that of suspended cells. Therefore, in microencapsulated PC12 cells, achievement of intra-capsule unfrozen condition during freezing leads to reducing the solution effect and improving the viability.

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