Hollow-fiber reactors, animal cell

The most advanced technology is the extracorporeal hollow fiber reactor. It is currently in Phase III trial and achieved a good Phase II record to support it. Other techniques including a polyurethane system devised in Japan and encapsulated hepatocytes from UCLA are or were in large animal trials. Whether a device is extracorporeal or is intended for implantation, clinical significance requires a suitable scaffold to support a sufficiently large colony of hepatic cells. For both extracorporeal and implant use, the physical structure of the scaffold must meet certain requirements of strength, void volume, biocompatibility, and other parameters. 

Hollow fiber modules are sometimes used to culture animal cells that are confined to the shell side of the module the separately oxygenated nutrient solution flows inside the fibers and perfuses the cells on the shell side. In the spiral membrane reactor (Fig. 17), the membrane that contains the immobilized enzyme is rolled into a spiral and confined within a shell. The feed or reactant solution flows in at one end and the product is removed from the opposite end of the cylindrical shell. 

There are many studies on how to determine fiber dimensions, spacing, and reactor length however, commercially available units come in a relatively limited number of sizes, usually with inner liber diameters of 500 /rm or more. Several reports in the literature describe the use of hollow-flber systems in the development of a bioartiflcial pancreas, which place the islets on the shell side, while perfusing the fibers with the animal s plasma or blood. The fibers can be made relatively non-thrombogenic and of porosity sufficiently small as to avoid immune attack of the cells inside the shell. One difficulty with this configuration is that interfiber distances in the hollow-fiber device are not well controlled, so that regions within the shell space receive too little nutrients. 

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