A cartridge should be selected based on the intended application. FiberCell® Systems offers three types of fibers: polysulfone, cellulosic, and PS+ fibers. We also offer three different molecular weight cut-offs (MWCO): 5 kd, 20 kd, and .1 micron.
The hydrophilic polysulfone fiber is specifically selected for good cell culture performance. Both the 5 kd MWCO and 20 kd MWCO fibers have ten times the gross filtration rate of the equivalent cellulosic fiber for rapid nutrient and waste exchange. This is seen as better cell growth and higher fidelity of protein production not seen in cellulosic fibers. Any cell type that will attach to plastic or grow in suspension culture should grow well in the polysulfone cartridge.
One unique feature of the FiberCell® Systems hollow fiber bioreactor is that the fibers are cast with little “waves”, resulting in an even distribution of the fiber bundle within the cartridge shell. The FiberCell® Systems hollow fiber bioreactors are the first bioreactors that are optimized for both adherent and suspension cells. The cellulosic fibers are generally not intended for use in cell culture, as their low gross filtration rate is not optimal for cell growth. They have specific applications for in vitro toxicology.
As a general rule the cartridge used will depend upon the size of the secreted product you wish to collect and the amount you wish to collect. FiberCell® Systems cartridges are powerful cell culture tools and their small size can be misleading. The medium sized C2011 with a surface area of 3,000 cm2 and a volume of only 20 mL has been shown to out-produce a 10 liter bag type bioreactor by a significant degree. The larger cartridges should only be used when 500 mg or more of a recombinant protein is desired.
At FiberCell® Systems, we define our molecular weight cut offs at the 50% retention mark as a convention. We also speak of the “useful retention” meaning the size of protein that will be retained by 90% or more. This depends upon the size, shape, post-translational modifications and stokes radius of the protein, not just the molecular weight. For the 5 Kd MWCO fiber we define the useful retention as 20 kd. It should be used for proteins in the range of 20 kd on up to about 140 kd. For larger proteins, the 20 kd MWCO fiber should be used. Since the gross filtration rate is so high there is no penalty (such as the requirement to feed the ECS) with using the 5 kd MWCO fiber though there may be a slight improvement in productivity when using the 20 kd fiber. Please see the recombinant protein section for more information.
For monoclonal antibody production the 20 kd MWCO fiber should be used to allow TGF beta to diffuse out while retaining the antibody within the small volume of the ECS. The scale-up option here is the C5011 which is optimized for hybridoma culture. Please see the monoclonal antibody section for more information.
The PS+ fiber has a unique chemistry that allows protein matrices, antibodies and cytokines to be bound to the surface of the fiber. This cartridge should be used for primary cell types where you wish to control the surface matrix that the cells interact with and also for the growth of endothelial cells on the inside of the fiber. The fiber must be coated with some matrix so this matrix should be taken into account when selecting this fiber.
Many other cell types have been cultured in the FiberCell® Systems hollow fiber bioreactor system. FiberCell® Systems can provide the benefits of a combined 20 years plus experience with working with these systems and would be happy to discuss your application.