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Toward synthetic kidneys and livers.

Toward synthetic kidneys and livers

Thomas M.S. Chang, director of McGill University's Artificial Cells and Organs Research Centre in Montreal, has spent 30 years developing tailor-made artificial cells to replace or augment specific functions performed by the body's own cells, such as clearing toxic substances from the blood. His living-cell-sized chemical-reaction centers encapsulate enzymes, detoxicants, peptides, even other cells within a semipermeable membrane. Now under design are multi-enzyme units to take over where his commercially available activated-charcoal-based blood-cleanup cells leave off. The new systems will convert the toxic urea and ammonia that build up in people with kidney and liver failure into useful amino acids.

The prototype cells -- 10 to 50 microns in diameter -- contain one enzyme (urease) to convert urea into ammonia, another (dehydrogenase) to transform ammonia into three essential amino acids (leucine, isoleucine and valine), and a "cofactor" that activates the dehydrogenase. A third enzyme (glucose dehydrogenase), which frees up the cofactor for reuse, completes the mix.

In test-tube experiments, the new cells converted 50 to 60 percent of the urea into amino acids within two hours. Further refinements underway should speed and increase the conversion, Chang told SCIENCE NEWS. The cells, which he says could be ready for animal testing within about nine months, will eventually be incorporated into a column through which blood is filtered. Chang believes these cells, together with the activated-charcoal-based cleanup cells, could function as artificial organs to convert into useful products the toxic wastes that build up in patients with liver or kidney failure.
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Author:Raloff, Janet
Publication:Science News
Date:Jun 25, 1988
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