Bead-to-bead transfer of Chinese hamster ovary cells using macroporous microcarriers

Chinese hamster ovary cells (CHO-K1) were cultivated in macroporous gelatin microcarriers (CultiSpher G and CultiSpher S) in spinner flasks and a 51 bioreactor. Near-to-confluent cultures were harvested by bead-to-bead transfer where intact microcarriers with cells were transferred from a spinner flask to another spinner flask or to the bioreactor with naked microcarrier beads. Successful bead-to-bead transfer was achieved in various split ratios. The duration of attachment seemed to be important where the direct contact of beads to each other can be achieved by intermittent stirring. Repeated transfers were performed and at least four transfers in spinner flasks were achieved. Two variations of bead-to-bead transfer were performed in the 51 bioreactor either by seeding the bioreactor with near-to-confluent beads cultivated in spinner flasks or in situ transfer by adding fresh beads to the bioreactor. As in the spinner case, attachment was achieved by intermittent stirring where donor beads were in close proximity to the acceptor beads. Again successful transfers were obtained as evidenced by the good growth on acceptor beads where cell yields were in the range of 3100-4500 cells/bead. The results suggest that bead-to-bead transfer of CHO-K1 cells can be easily performed and do provide an alternative route to applications where dissolution techniques may not offer an efficient solution.