Northwestern University researchers have developed the first electronic device for continuously monitoring the health of transplanted organs in real time.
Sitting directly on a transplanted kidney, the ultrathin, soft implant can detect temperature irregularities associated with inflammation and other body responses that arise with transplant rejection. Then, it alerts the patient or physician by wirelessly streaming data to a nearby smartphone or tablet.
In a new study, the researchers tested the device on a small animal model with transplanted kidneys and found the device detected warning signs of rejection up to three weeks earlier than current monitoring methods. This extra time could enable physicians to intervene sooner, improving patient outcomes and wellbeing as well as increasing the odds of preserving donated organs, which are increasingly precious due to rising demand amid an organ-shortage crisis.
The study is published in the journal Science.
Rejection can occur at any time after a transplant — immediately after the transplant or years down the road. It is often silent, and patients might not experience symptoms, the study authors said.
“I have noticed many of my patients feel constant anxiety — not knowing if their body is rejecting their transplanted organ or not,” said Dr. Lorenzo Gallon, a Northwestern Medicine transplant nephrologist, who led the clinical portion of the study. “They may have waited years for a transplant and then finally received one from a loved one or deceased donor. Then, they spend the rest of their lives worrying about the health of that organ. Our new device could offer some protection, and continuous monitoring could provide reassurance and peace of mind.”
Northwestern’s John A. Rogers, a bioelectronics pioneer who led the device development, said it’s critical to identify rejection events as soon as they occur.
“If rejection is detected early, physicians can deliver anti-rejection therapies to improve the patient’s health and prevent them from losing the donated organ,” Rogers said. “In worst-case scenarios, if rejection is ignored, it could be life threatening. The earlier you can catch rejection and engage therapies, the better. We developed this device with that in mind.”
“Each individual responds to anti-rejection therapy differently,” said Surabhi Madhvapathy, a graduate student in Rogers’ laboratory and the paper’s first author. “Real-time monitoring of the health of the patient’s transplanted organ is a critical step toward personalized dosing and medicine.”
Gallon also is a professor of nephrology and hypertension and organ transplantation at Northwestern University Feinberg School of Medicine. Rogers is the Louis Simpson and Kimberly Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at Northwestern’s McCormick School of Engineering and director of the Querrey Simpson Institute for Bioelectronics (QSIB). Gallon and Rogers co-led the study with Dr. Jenny Zhang, a research professor of organ transplantation at Feinberg.
Current monitoring challenges
For the more than 250,000 people in the U.S. living with a transplanted kidney, monitoring their organ’s health is an ongoing journey. The easiest way to monitor kidney health is through measuring certain markers in the blood. By tracking the patient’s creatinine and blood urea nitrogen levels, physicians can gain insight into kidney function. But creatinine and blood urea nitrogen levels can fluctuate for reasons unrelated to organ rejection, so tracking these biomarkers is neither sensitive nor specific, sometimes leading to false negatives or positives.
The current “gold standard” for detecting rejection is a biopsy, in which a physician uses a long needle to extract a tissue sample from the transplanted organ and then analyzes the sample for signs of impending rejection. But invasive procedures like biopsies carry risks of multiple complications, including bleeding, infection, pain and even inadvertent damage to nearby tissues.
Other new blood biomarkers can be used in tandem with monitoring patients' creatinine and blood urea nitrogen levels, but these have suboptimal positive predictive values.
“The turnaround time can be quite long, and they are limited in monitoring frequencies and require off-site analysis,” Gallon said. “It might take four or five days to get results back. And those four or five days could be crucial in making a timely decision for the care of the patient.”