| Description |
The technologies and processes used in large scale cell bioprocessing, namely the impeller based stirred suspension bioreactor, were designed for the growth of robust and often immortal cell lines to produce protein based therapeutics. The turbulent fluid environment created by such systems was not designed to accommodate the delicate nature of stem cell suspension culture - in particular, to maintain the low shear stress and homogeneity required to retain an undamaged cell and unaltered phenotype. While new bioreactor designs have been developed to address the unique environmental needs of stem cell cultures, industrial volume scale-up is still unavailable. In this work, a novel biomimetic mixing mechanism utilizing a silicone diaphragm and an alternating actuation mechanism has been designed and developed to produce adequate fluid mixing while maintaining a low shear stress environment. The unique design, characterized on a bench-top scale, has been scaled-up over a range of volumes from 100 - 3000 ml. Using particle image velocimetry, the fluid dynamics created by the novel mixing mechanism were qualitatively and quantitatively analyzed. The mixing mechanism produced adequate fluid mixing within the vessel while maintaining mean shear stress levels more than 100 times lower than seen in impeller based spinner flasks. Furthermore, the mixing profile and mean shear stress levels remained well below requirement levels regardless of reactor volume. In conclusion, we have developed a novel mixing system which overcomes shear stress limitations of current stirred suspension reactors in volumes ranging from 100-3000 ml. |
