Researchers have developed an important part of the first fully functioning artificial kidney for patients with end-stage renal disease. Using nanotechnology, they've created a human nephron filter the size of a paperback book-small enough to be portable or implantable.

The experimental equipment has two membranes that work in series within one cartridge. The first membrane performs the function of the glomerulus, the second mimics the renal tubules. The membranes filter and process blood, discharging waste and water into a bag (an external bladder) and returning substances such as sodium, calcium, and nutrients to the body. Patients using the device wouldn't need dialysis or kidney transplantation.

In computer model tests, the researchers found that operating 12 hours per day for 7 days, the device offers a glomerular filtration rate of 30 ml/minute. Conventional hemodialysis performed three times per week provides a filtration rate that's half that amount.

Future work will involve building a complete membrane, testing it on animals, and testing it in humans. Clinical trials could start by 2010.

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