FIG. 1.

Effect of storage temperature for up to 1 year on viability of encapsulated liver cell spheroids (ELS) at 24 h in postwarming cultures. ELS were thawed, and viability was assessed at 24 h postwarming. Micrographs (top) show fluorescein diacetate (FDA) (alive) and propidium iodide (PI) staining (dead) after storage time indicated. Images captured: ×4 original magnification, 64 ms exposure FDA, and 250 ms exposure PI. Viability of ELS stored either at −170°C (dark bars) or at −80°C (light bars) was quantified using image analysis. For the −80°C stored samples, a clear deterioration over time was observed, to a minimum after 12 months. **p<0.01, ***p<0.005–170°C compared to −80°C at the same time point; aaa p<0.005 cf. 1-month storage at −80°C, b p<0.05 cf. 2-month storage at −80°C and p<0.005 cf. 1-month storage at −80°C, c p<0.05 cf. 6-month storage at −80°C and p<0.005 cf. 1-,2-, and 3-month storage at −80°C, ddd p<0.005 cf. 1-,2-,3-, and 6-month storage at −80°C.