Bluetooth-enabled device warns if body rejects a new organ

The device is the size of a fingernail, is Bluetooth-enabled, and has a coin battery.
Sejal Sharma
The device is the size of a small coin
The device is the size of a small coin


After an organ transplant, the body either accepts the organ or rejects it. All patients have some amount of acute rejection, but hyperacute rejection is when the body vehemently rejects the organ and it must be removed immediately to save the life of the patient. And then there’s chronic rejection, which can take many years as the body's immune response towards the new organ slowly damages the transplanted tissues or organ.

So, how do we detect early on that an organ transplant has failed? The gold standard is currently via a biopsy, performed periodically to detect rejection early before symptoms develop.

But what if there was a less invasive procedure that could tell us about a possible transplant failure? Researchers at Northwestern University have developed a device that can give real-time information about the surgical recovery of a transplant.

Bluetooth-enabled device warns if body rejects a new organ
The device attached to the kidney of a mouse

The device monitors temperature

The implant, tested in an animal model on mice, can continuously monitor transplanted organs (kidneys in this case) by tracking their temperature. When the temperature changes, an alert is sent to a smartphone or tablet in real time.

“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,” said John A. Rogers, who led the device development.

“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,” he added.

60% of transplants in the US are kidney transplants

The sensor is the size of a baby’s fingernail. It is just 0.3 centimeters wide, 0.7 centimeters long, and 220 microns thick. How, then, did the team attach the sensor to the mouse's kidney? They banked on the kidney’s natural fibrous layer, called the renal capsule, which surrounds and protects the organ from damage. The sensor is designed to fit just beneath the capsule layer, where it attaches to the kidney. 

The device has a sensitive thermometer that can detect the slightest change in temperature and has a coin-cell battery to power it. It uses Bluetooth technology to continuously stream data to external devices. The device can also monitor the impact of medications, circadian rhythms, activity, and graft rejection.

How does the device work?

There are certain tell-tale signs that a patient’s immune system hasn’t fully adapted to a new organ. In rare cases, there might be general discomfort, ill feeling, body chills, flu-like symptoms, or pain or swelling around the organ.

But in many cases, these symptoms arrive too late. The new device can detect warning signs of rejection, such as an increase in temperature – two to three weeks earlier than changes in the blood serum creatinine test – a standard test that tells about the health of kidneys, as per the study. This was true in mice that were on immunosuppressant medications. Real-world kidney transplants require immunosuppression treatment to inhibit graft rejection so that the body’s ability to reject an organ is lowered.

In animals without immunosuppressant medications, temperatures increased two or three days before biomarkers changed in blood samples.

“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,” added Dr. Gallon.

The researchers are now planning on testing their device on a larger animal model. They are assuming for now that since their device worked on kidneys, it could also work for other transplanted organs like the liver and lungs.

The study is published in the peer-reviewed journal Science.

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