Wearables May Provide Early Kidney Health Warning Signs

Bridget M. Kuehn
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Over the past 15 years, John Rogers, SM, PhD, executive director of Northwestern University's Querrey Simpson Institute for Bioelectronics in Evanston, IL, has been working on translating modern electronics technology into wearable or implantable medical devices.

He is attempting to reformulate the hard, brittle, silicone components that have turned mobile devices into powerful pocket computers into flexible materials that clinicians could use on or in the human body. These devices can function as wearable “second skin” or lie on the surface of an organ, such as the brain, heart, or kidney, and capture clinical-grade measurements to drive research breakthroughs or clinical care innovation.

“We're aiming to drive progress at the boundaries [among] engineering, science, and medical science,” said Rogers, who is also the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Bio-medical Engineering and Medicine at Northwestern's McCormick School of Engineering. “We are envisioning a future where electronics adopt physical properties that are compatible with soft tissues and living systems.”

Devices developed by Rogers are already monitoring health data in thousands of people around the globe. Now, he is working on two projects that could change how nephrologists monitor kidney function in patients with kidney disease or identify signs of kidney transplant rejection, according to his State-of-the-Art presentation at Kidney Week 2022.

Global reach

Rogers and his team have developed electronics that mimic the skin's thickness and mechanical, thermal, and water-permeation properties. They have used this technology to create a portfolio of wireless devices useable almost anywhere on the body. The devices can be used individually or integrated to provide full-body health-status assessments in the hospital or at home.

“You can think of these devices almost like a second skin that can go on your natural skin in a way that is physically imperceptible to the patient…that allows for quantitative clinical-grade measurements,” Rogers said.

Working with colleagues in the neonatal intensive care units and pediatric intensive care units at the Ann & Robert H. Lurie Children's Hospital of Chicago and Prentice Women's Hospital, Rogers developed and tested these devices to monitor vital signs in newborns (1). One sticker-like device on the chest measures electrocardiogram and temperatures and can help measure respiration and heart rate. A second device, wrapped around the foot, continuously measures blood oxygenation. When the two devices are synchronized, they can monitor blood pressure or blood flow.

“The two devices are monitoring all of the vital signs currently captured today with cumbersome, high-cost, wire-based biosensors,” Rogers said. In 2021, a startup company, called Sibel Health, launched by Rogers and colleagues, received US Food & Drug Administration (FDA) clearance for the device (2).

In partnership with the Bill & Melinda Gates Foundation, Save the Children, Merck for Mothers, and the Steele Foundation for Hope, Rogers and his team deployed this technology to monitor the vital signs of more than 15,000 mothers and infants living in lower resource settings in Kenya, Ghana, Zambia, India, Pakistan, and Mexico (3). The battery-powered devices upload the data they collect to a privacy-protected Cloud-based platform where clinicians can remotely analyze them.

A collaboration between Rogers and neurosurgeons at Northwestern resulted in the creation of a device to measure cerebrospinal fluid flow in children who have a shunt to remove excess brain fluid buildup (4). The team designed the tool to help patients determine if their shunt is working. Patients with a shunt who experience nonspecific symptoms, such as a headache or nausea, which can indicate a life-threatening emergency, shunt failure, or a more benign condition, must rush to the emergency department for assessment. However, the new tool uses tiny heaters and temperature sensors in a skin-like device to measure the fluid flow. “It turned out to be very easy to do,” Rogers said. “We could immediately see if there's flow or no flow.”

Rogers said that the team launched another company, called Rhaeos, Inc., to develop the shunt-monitoring device (5) and is conducting clinical trials necessary to gain FDA clearance for the device.

Kidney applications

Rogers is also working with Lorenzo Gallon, MD, medical director of the Translational Medicine program and director of the Transplant Nephrology Fellowship at Northwestern, to create implantable sensors to detect the earliest signs of kidney transplant rejection. The goal is to be able to treat patients as early as possible and avoid the need for a biopsy.

“The hypothesis was that if you are undergoing a rejection, then the transplanted kidney would likely increase in temperature, and there might be an increase in blood flow associated with that rejection event,” Rogers said.

They have created an implantable, wireless sensor that attaches to the kidney and measures blood flow and temperature. After testing the device in rats, they found that temperature—but not blood flow—provides an early warning about rejection. Now, they have begun testing the device in pigs. The new version of the device attaches to the kidney with a tiny barb, can also measure blood oxygenation, and uses a wirelessly recharged battery.

The skin-like sensors that Rogers and his team have created can also be used to measure compounds in sweat to assess hydration. The team is marketing the Gx sweat patch in stores through a partnership with Gatorade. Rogers created a version of the device for the National Kidney Foundation's 2017 “Heart Your Kidneys” promotional event at South by Southwest (6). The team has also created a color-changing sticker version of the device, which provides an easier, less cumbersome approach than existing wearables, that clinicians are using at Lurie Children's Hospital to measure sweat chloride levels to screen for cystic fibrosis.

They have since worked to develop a skin sensor that can measure creatinine, urea, and pH in sweat. The vision is to enable at-home kidney screening, but first, the team needs to understand how sweat creatinine levels correspond with those in urine or blood.

“That's a topic of ongoing research,” Rogers said. He said he hoped his talk at Kidney Week would lead to feedback about the potential kidney applications he is developing and perhaps generate new collaborations.