Propellers Were Invented in 1830...
Not recommended for stem cells.
Propellers are by their very nature, turbulent devices. They create a flow across a blade element causing fluid, particles and cells to be accelerated, compressed and passed through pressure and velocity differentials that are very turbulent. Mixing is a chaotic event with a propeller and results in an uneven distribution of cells, gas and nutrients.
Propellers create dead zones just under the hub of the propeller. Differing circulatory zones develop in the vessel; two beside the drive shaft, one on the surface and perhaps two more at the perimeter of the propeller. In small vessels, at slow speeds, this may work with some materials. However, when live cells and vaccines are the subject of the mixing effort, scale up is severely compromised by the use of a propeller. The reasons are many.
As one increases the diameter of the propeller in an effort to scale up, tip speed becomes an issue. To compensate, users typically reduce the speed of the propeller and add another propeller to the shaft in order to provide the mixing energy required for a vessel. Now with two propellers, more zones of turbulence develop and the internal dynamics of the vessel become even more chaotic.
Simply stated, stem cells will not grow in a two propeller vessel and therefore propellers are not a scale up option in this new field of regenerative medicine and are becoming increasingly problematic in many vaccine applications.
Eliminate Scale Up Barriers
Scale up has always been the most critical issue in mixing technology. The results achieved by a propeller in 250 ml vessel and what is actually achieved in a 200 litre vessel, are overwhelming different.
With some materials, such as paint or water, mixing specialists approach the problem by using a bigger propeller, or using multiple propellers, or by using baffles to prevent vortexing.
In shear sensitive cell based bioreactors, the solutions of the past fail to provide effective results. The present reality therefore, is that the limitations of propeller technology, serves to dictate and moreover restrict, the size of mixing vessel that can be used. It stands to reason that there is no working 50 litre stem cell bioreactor--- anywhere. The BACH impeller will effectively change the landscape by eliminating this scale up barrier.
The BACH impeller uses the fluid to mix the fluid.
It uses a pre whirl event to start the vessel contents moving and once the fluid flow is setup, the internal velocity differentials and pressure differentials become constant. Sudden acceleration and deceleration zones become a relic of the past. Tip speed becomes an irrelevant variable. The BACH impeller mates the speed at which the cell is moving with the speed of the fluid that is carrying it, because the fluid itself is doing the mixing.
The BACH impeller uses an internal, compound log spiral hub to compensate for material entering the impeller and preventing it from decelerating too fast.
Want to use a bigger vessel? Just scale up the size the vessel and use an impeller that is one third the diameter of your bioreactor. It is simple. Scale up just doesn’t have a barrier anymore.
Be A Part Of The Evolution
Mixing has been a part of the industrial revolution for almost 150 years and has been based primarily on marine propeller technology. Agitation and blending are synonymous with propeller mixers and they have been used in the manufacture of paints, chemicals and food for those 15 decades.
Propeller design has done well in both propulsion, pumping and mixing, however over the past 2 decades and more importantly the last 10 years, we have seen material science mature. Ultra shear sensitive polymers, nano particle suspension, and of course, cell based solutions that will change the landscape of biotechnology, have all emerged into focus.
Evolution is the process of adaptive change prompted in response to changes to the environment.
The BACH impeller allows the principles of mixing to evolve and brings solutions to biotech that no propeller or turbine can provide. Propellers damage cells. Propellers make cell attachment difficult. Propellers dictate bioreactor size. In short, propellers limit what can be provided to the world’s population in the form of cell based health solutions.
The BACH impeller represents the evolutionary bridge to the future of of cell based health solutions.
Eliminate Scale Up Barriers
Scale up has always been the most critical issue in mixing technology. The results achieved by a propeller in 250 ml vessel and what is actually achieved in a 200 litre vessel, are overwhelming different.
With some materials, such as paint or water, mixing specialists approach the problem by using a bigger propeller, or using multiple propellers, or by using baffles to prevent vortexing.
In shear sensitive cell based bioreactors, the solutions of the past fail to provide effective results. The present reality therefore, is that the limitations of propeller technology, serves to dictate and moreover restrict, the size of mixing vessel that can be used. It stands to reason that there is no working 50 litre stem cell bioreactor--- anywhere. The BACH impeller will effectively change the landscape by eliminating this scale up barrier.
The BACH impeller uses the fluid to mix the fluid.
It uses a pre whirl event to start the vessel contents moving and once the fluid flow is setup, the internal velocity differentials and pressure differentials become constant. Sudden acceleration and deceleration zones become a relic of the past. Tip speed becomes an irrelevant variable. The BACH impeller mates the speed at which the cell is moving with the speed of the fluid that is carrying it, because the fluid itself is doing the mixing.
The BACH impeller uses an internal, compound log spiral hub to compensate for material entering the impeller and preventing it from decelerating too fast.
Want to use a bigger vessel? Just scale up the size the vessel and use an impeller that is one third the diameter of your bioreactor. It is simple. Scale up just doesn’t have a barrier anymore.
We Solve Cell Attachment Issues
It’s simple math.
The BACH impeller running at 140 rpm in a 3 litre vessel, has overall internal velocities that are HALF that of a propeller running at 90 rpm.
The local velocities produced by the BACH impeller are constant. A cell attached to a micro carrier that is rotating around a vessel, does not have to deal with another cell next to it, attached to micro carrier, that is going at a significantly different speed.
The ability of the BACH impeller to materially reduce internal velocities, eliminates the effects of shear force experienced with the use of propellers. The BACH impeller prevents development of layers or streams of fluid that travel across other layers or streams of fluid going at a different speeds, or in different directions. Shear stress is eliminated with the BACH impeller.
How?
A propeller is a very turbulent device. It mechanically thrashes through fluid. It does this by sucking fluid in one side, forcing the fluid over its blade and ejecting the fluid out the other side.
The BACH impeller uses the fluid itself to do the mixing. The impeller creates a fluid flow that is stable, fairly predictable, homogenous and self adapting to the vessel size. Importantly, it creates a single mixing zone in a bioreactor, with the result that gradients become a thing of the past. Also, because it moves fluid 5x faster than a propeller, a change in pH, temperature, or KLA are easily solved in very short times.
Cell attachment is difficult to achieve in many small bioreactors. Establishing a bond between a cell and a microcarrier on such a small scale, while moving fluid quickly enough, is promoted by the reduction of mechanical stress in a bioreactor that employs a BACH impeller. It is an important feature of the BACH impeller that it allows for the fluid itself to do the mixing, rather than the mechanical thrashing of a propeller . It is widely known that use of propellers impede cell attachment and also cause cell deformity.
Achieve Perfect Cell Distribution
Pre vial filling - Post harvest of cells requires an intermediate “station” to keep harvested cells in suspension. It is critical that the mixing is non destructive and the cells are 100 percent heterogeneous in this vessel. Only then can you eliminate the bottleneck of cell count and fill each vial with the same amount of cells.
Perfect cell distribution is also critical for T-cell production. Gradients must be eliminated and nutrients and gas levels kept uniform throughout the bioreactor.
