The Fibra-Cel disks are a solid support material for the growth of animal and plant cells. The disks are used in the packed-bed basket of the NBS cell culture bioreactors/fermentors and spinners, CelliGen and the CelliGen Plus bioreactors. Animal cells such as hybridoma, insect and anchorage-dependent recombinant cells have all been successfully grown in the CelliGen Plus bioreactor using Fibra-Cel. | Back to top

Why are Fibra-Cel disks used?

The disks are used as a matrix for the growth of cells when secreted products are desired. The main advantages are: low pressure drop across the bed for efficient scale-up, higher surface-to-volume ratios, less susceptibility to shear forces from impeller blades and sparger gas bubbles, higher mass transfer of nutrients and oxygen, as well as cell growth and separation of secreted products in a single step. | Back to top

How do results with Fibra-Cel compare with that of microcarriers or other supports?

Cell density and productivity achieved with cells growing on Fibra-Cel disks are approximately ten times higher than anchorage-dependent cells growing on microcarriers (or even yields of suspension cultures). Currently, researchers are reporting growth for most cell lines of 108 cells per cm3 of bed volume. In a study of a mouse-mouse hybridoma producing an IgG monoclonal antibody, 0.5 grams MAb per liter of bed volume were produced per day in a packed-bed basket using serum-free medium as well as medium containing 1% serum. (Cytotechnology 9:41-49, 1992). In another study concerning growth of CHO cells on Fibra-Cel in the CelliGen Plus basket, final density of 9.5 x 107 cells per mL was achieved, and t-PA activity increased 14 times compared to growth in a stirred-tank reactor using microcarriers. | Back to top

Which support is more effective in reducing operating costs?

Fibra-Cel offers the added benefit of sustaining long-term periods of high-density growth in perfusion. There is never any danger of clogging. Higher cell densities and productivities coupled with reduction in downstream processing also lowers overall production costs. Elimination of cell filtration (including spin filters), lowers costs still further. Cells immobilized in the matrix serve as a renewable catalyst for continuous production of proteins. Fresh medium is fed into the bioreactor, washing secreted products through the matrix into the cell-free environment. Foam is virtually non-existent and there is no aggregation of beads to contend with. | Back to top

What is Fibra-Cel made of?

Fibra-Cel is made of polyester non-woven fiber and polypropylene. It is a 50/50 mixture by volume of these materials which are FDA-validatable in their original form. No other compounds are used. | Back to top

How is Fibra-Cel manufactured?

Fibra-Cel is manufactured according to GMP guidelines. Flat sheets of non-woven polyester and polypropylene mesh are ultrasonically bonded together and die-cut into 6 mm diameter disks. Then the disks are methanol-washed and electrostatically treated to produce a net binding charge. | Back to top

How long do cells take to attach to Fibra-Cel?

It takes approximately one hour for cells to attach to the fibrous disk, compared to approximately six hours for microcarriers. The growth process for microcarrier cultures can require extended delays for periodic stoppage of stirring to allow time for cells to become attached. By comparison, the Fibra-Cel packed bed is inoculated in a single step, and the process need not be stopped at any time. | Back to top

Why are yields with Fibra-Cel superior to that of other supports?

A number of cell lines have difficulty attaching to the surface of microcarriers. Cell lines such as MRC5 often require ideal conditions of temperature in order to attach cell viability. MRC5 as well as most other cell lines attach more readily to the flat surface of the Fibra-Cel disk because they become imbedded in the fiber system and cannot fall off as they do from the spherical surfaces of suspended beads. | Back to top

What causes a reduction in the attachment of cells to microcarriers?

There are several reasons for this. One concerns the leaching of toxins from microcarriers (see next question). Another reason is the belief held by some scientists that microcarriers require cell-to-cell interaction for growth to reach confluency on the bead. If cell attachment on the bead is sparse, the few cells that do attach initially will not survive. | Back to top

Can poor cell attachment on microcarriers be remedied by an increase in microcarrier concentration?

Researchers will sometimes increase microcarrier inoculum density to compensate for an anticipated low rate of cell attachment. Unfortunately, there is some leaching of toxins from microcarriers, and an increase in microcarrier density only serves to increase toxicity and further impair cell attachment. On the other hand, Fibra-Cel is a pure material that does not leach toxins. | Back to top

Is Fibra-Cel's successful performance achieved only with an inoculum containing healthy cells?

It makes no difference with Fibra-Cel. We have demonstrated that unhealthy cells which do not attach to microcarrier beads will attach and grow on Fibra-Cel disks, recovering to normal health in a short period of time. | Back to top

What type of toxicity tests are performed?

Testing for the presence of endotoxins in the materials is performed according to USP Title XXII, Chapter 85, page 1493. | Back to top

Why are the Fibra-Cel disks electrostatically treated?

This allows suspension cells such as hybridoma and insect to adhere to the disks and become trapped in the fiber system where they remain throughout the process. The electrostatic charge is similar to the binding charge to which plastic tissue cultureware is exposed. | Back to top

Is the use of Fibra-Cel Disks limited to anchorage-dependent cells?

Not at all. Suspension cells can also be propagated on Fibra-Cel, and to an even greater density than can be attained in suspension culture. Since the disks are electrostatically charged they promote adherence of suspension cells in the matrix. | Back to top

Can shear-sensitive cells be subjected to increased agitation without reducing cell growth and productivity?

Using packed-bed technology, cells entrapped in the Fibra-Cel matrix are shielded from the turbulence of impeller rotation and sparged gases. Shear forces are kept to a minimum in the basket, allowing higher rates of agitation which results in increased mass transfer of oxygen and nutrients. High medium flow rates and high mass transfer rates are among the main reasons for the superior performance of the Fibra-Cel packed-bed technology. | Back to top

Which cells have been successfully grown on Fibra-Cel disks?

Hybridomas, Anchorage-Dependent and Insect Cells. There has been a 100% success rate with every cell line cultured on Fibra-Cel disks. | Back to top

Are inoculation requirements the same for Fibra-Cel as they are for microcarriers?

With Fibra-Cel, requirements are less stringent, needing one-third less inoculum density than microcarrier cultures. Cells attach more readily to Fibra-Cel disks which are flat and immobile compared to microcarrier beads which are round and in constant motion. | Back to top

Is Fibra-Cel autoclavable?

Fibra-Cel can be autoclaved without any adverse effects on the efficacy of the material. The disks are loaded into the basket of the bioreactor and autoclaved in-situ. | Back to top

Are Fibra-Cel disks reusable?

The reuse of disks is not recommended. Microcarriers are not reused and neither are Fibra-Cel disks. | Back to top

Can Fibra-Cel be used for the production of biomass?

This application is not recommended since it requires trypsinization for removal of anchorage-dependent cells from the matrix. However, cells are recoverable from Fibra-Cel for analysis. For the growth of anchorage-dependent cells for biomass production the use of microcarriers is frequently preferred. Suspension cells can be covered by centrifugation. | Back to top

Is it possible to scale up a bioreactor with a Fibra-Cel packed-bed basket insert?

The design of the basket permits efficient and simplified scale-up due to the low pressure drop and low mass transfer resistance across the Fibra-Cel bed. Analysis of the cells located at the bottom of the bed indicate that they are as viable as the cells located at the top. These findings point to the uniform mass transfer of nutrients and oxygen in the Fibra-Cel basket system. Basket technology using Fibra-Cel disks has been successfully scaled up to 30 liters. (Application requests available upon request.) | Back to top

Are Fibra-Cel disks medical-grade certified?

Yes they are. Fibra-Cel is a USP Class VI material. | Back to top

I understand that NBS' Fibra-Cel disks can increase protein yields from animal cells by ten-fold or more, but can I recover my cells from the disks?

Yes you can, although Fibra-Cel was not developed with that purpose in mind. Anchorage-dependent cells will attach firmly to the disks, requiring trypsination for removal of the cells from the disk bed. Some cells are easier to detach than others. Suspension cells can be more easily recovered, typically via centrifugation. | Back to top

What is the thickness of Fibra-Cel disks?

The thickness for polyester non-woven fiber and polypropylene is 0.017 and 0.020 inch, respectively. | Back to top

Can I see live, unstained cells growing inside the Fibra-Cel disks using inverted microscope with phase contrast?

It is very hard to see live, unstained cells growing inside the disks using an inverted microscope with phase contrast, because the Fibra-Cel disks are not transparent. | Back to top

Can the cells on the Fibra-Cel disks be stained with fluorochrome-labeled antibodies and nuclear dyes (DAPI, Propidium)?

Yes, it is possible to stain the cells on Fibra-Cel disks with fluorochrome-labeled antibodies and nuclear dyes. | Back to top