New article about implantable kidney

Implantable artificial kidney based on microchips sees major progress
Written by Catharine Paddock PhD
Published: Wednesday 17 February 2016

An implantable artificial kidney could transform prospects for people whose kidneys have failed and who have to rely on dialysis or the rare chance of a transplant to stay alive. Now, researchers working on the first-of-its-kind device that aims to meet this need says they are hopeful of running pilot trials in humans within the year.
Microchip filter
The researchers plan to start pilot trials of the microchip filter in dialysis patients by the end of 2017.
Image credit: Vanderbilt University

Kidneys are amazing instruments that work 24/7 to clean blood and dispose of waste. Every day, these bean-shaped, fist-sized organs that sit either side of spine just under the rib cage filter around 150 liters of blood to produce 1-2 liters of urine.

Transplant is the best treatment for kidney failure but demand for organs is huge compared with supply.

The US Organ Procurement and Transplantation Network say there are over 100,000 patients on the waiting list for a kidney transplant, but last year, only 17,108 received one.

In all, the National Kidney Foundation estimate that over 460,000 Americans have end-stage kidney disease, and every day, 13 people in the US die waiting for a donor kidney. They say the federal Medicare bill for caring for kidney disease patients - excluding prescription drugs - was around $87 billion in 2012.

William H. Fissell IV, a kidney specialist and associate professor of medicine at Vanderbilt University Medical Center in Nashville, TN, and his team hope to put an end to this devastating scenario, as he explains:

"We are creating a bio-hybrid device that can mimic a kidney to remove enough waste products, salt and water to keep a patient off dialysis."

The goal is to make a device that is small enough - about the size of a soda can - so it fits inside a patient's body.

The implantable artificial kidney contains microchip filters and living kidney cells and will be powered by the patient's own heart.
Silicon nanotechnology plus living kidney cells

The microchip uses the same silicon nanotechnology that the microelectronics industry uses for computers.

Prof. Fissell says the chips are inexpensive, precise and make ideal filters. Each device will contain about 15 microchips, one on top of the other.

Each microchip filter contains pores, each of which will contain and act as a scaffold for a membrane of living kidney cells that mimic the natural functions of the kidney. The team is designing the filter one pore at a time to do precisely what they want each to do.

Prof. Fissell says fortunately the cells grow well in the lab dish. They can create a membrane of kidney cells that can work out which compounds in the blood reabsorb as nutrients that stay in the blood, and which have to be removed as waste products destined for disposal in urine.

This way, says Prof. Fissell, "we can leverage Mother Nature's 60 million years of research and development," to create a bioreactor of living cells at the heart of the artificial kidney.
Powered by patient's blood flow without risk of clots

The device does not require a source of power because it uses the power of the patient's heart - the natural pressure of blood flow in the blood vessels - to push the blood through the filters.

However, this feature also presents a challenge: how to fine-tune the fluid dynamics so blood flows through the device without clotting.

Dr. Amanda Buck, a biomedical engineer with an interest in fluid mechanics, is in charge of this part of the project.

Dr. Buck uses computer models to refine the shape of the channels inside the device to achieve the smoothest blood flow. Then, with the help of 3D printing, the team creates a prototype and tests it to see how smoothly blood flows through it.

Prof. Fissell says because the bio-hybrid device will be out of reach of the body's immune response, it is unlikely to incur rejection. "The issue is not one of immune compliance, of matching, like it is with an organ transplant," he explains.
Over a decade of research coming to fruition

The kidney project started over a decade ago. In 2003, it attracted its first grant from the National Institutes of Health (NIH), and the NIH have recently awarded a 4-year, $6 million grant to Prof. Fissell and his research partner and long-time collaborator Shuvo Roy, from the University of California-San Francisco.

In 2012, the Food and Drug Administration (FDA) granted the project fast-track approval - a status the federal regulator reserves for treatments that address serious or life-threatening conditions and show potential to fill unmet medical needs.

The team is hoping to run pilot trials of the silicon filters by the end of 2017. Prof. Fissell says he has a long list of patients eager to participate, and he declares his admiration for them as he concludes:

"My patients are absolutely my heroes. They come back again and again and they accept a crushing burden of illness because they want to live. And they're willing to put all of that at risk for the sake of another patient."

In the following video that takes a look inside the artificial kidney, Prof. Fissell explains how they are designing to keep patients off dialysis:
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