Expanding cells in a bioreactor
Described are embodiments for expanding cells in a bioreactor. In one embodiment, methods are provided that distribute cells throughout the bioreactor and attach cells to specific portions of a bioreactor to improve the expansion of the cells in the bioreactor. Embodiments may be implemented on a cell expansion system configured to load, distribute, attach and expand cells.
1. A method of loading cells in a cell expansion system, the method comprising:
circulating fluid at a first flow rate through a bioreactor of a cell expansion system, wherein the fluid comprises a plurality of cells;
reducing circulation of fluid from the first flow rate to about 0 ml/min;
maintaining the bioreactor in a first orientation for a first predetermined period of time to allow at least a first portion of the plurality of cells to settle;
after the first predetermined period of time,
circulating fluid at a second flow rate through the bioreactor, wherein the second flow rate is slower than the first flow rate;
reducing the circulation of fluid from the second flow rate to about 0 ml/min;
maintaining the bioreactor in a second orientation for a second predetermined period of time to allow at least a second portion of the plurality of cells to settle; and
expanding at least the first and the second portion of cells in the bioreactor.
2. The method of claim 1 , further comprising:
after the first predetermined period of time and before the circulating fluid at the second flow rate:
rotating the bioreactor to the second orientation that is about 180 degrees from the first orientation.
3. The method of claim 2 , further comprising:
after the second predetermined period of time and before expanding, rotating the bioreactor about 180 degrees to the first orientation.
4. The method of claim 1 , further comprising:
after the second predetermined period of time:
circulating fluid at a third flow rate through the bioreactor, wherein the third flow rate is slower than the second flow rate;
reducing a rate of circulation of fluid from the third flow rate; and
maintaining the bioreactor in the second orientation for a third predetermined period of time to allow at least a third portion of the plurality of cells to settle.
5. The method of claim 4 , further comprising:
after the third predetermined period of time:
circulating fluid at a fourth flow rate through the bioreactor, wherein the fourth flow rate is slower than the third flow rate; and
reducing circulation of fluid from the fourth flow rate; and
maintaining the bioreactor in the second orientation for a fourth predetermined period of time to allow at least a fourth portion of the plurality of cells to settle.
6. The method of claim 5 , wherein the first period of time, the second period of time, the third period of time, and the fourth period of time are the same.
7. The method of claim 1 , wherein the first period of time and the second period of time are equal in duration.
8. The method of claim 1 , wherein the first period of time is less than about 10 minutes.
9. The method of claim 8 , wherein the first period of time is less than about 8 minutes.
10. The method of claim 1 , wherein the bioreactor comprises a hollow fiber membrane.