Sensor warns of graft rejection three weeks before the first symptoms appear
Engineers have developed a wireless device to monitor in "real time" the health of transplanted organs.Researchers at Northwestern University have developed the first electronic device to continuously monitor the health of transplants. An ultrathin soft implant placed on a transplanted kidney detects temperature fluctuations associated with inflammation and other body reactions that occur during rejection. The data is wirelessly streamed to a smartphone or tablet.
The sensor is 0.3 centimeters wide, 0.7 centimeters long, and 220 microns thick. The device is smaller than a fingernail on the little finger and its thickness is comparable to a human hair. To attach the device to the kidney, the engineers used the natural biology of this organ. The kidney is covered by a fibrous layer, the renal capsule, which protects the organ from damage. The sensor is placed under the capsule and fits snugly against the kidney.
The device contains a highly sensitive thermometer that detects small changes in kidney temperature (accurate to 0.004 °C). The device also measures blood flow, but experiments have shown that temperature is a better predictor of rejection. The device runs on a tiny electric battery and uses Bluetooth technology to continuously wirelessly transmit data to external devices.
The scientists tested the device's performance on rats with transplanted kidneys. The analysis showed that the local temperature of the graft increased (sometimes by 0.6 °C) - before rejection. In animals that did not receive immunosuppressants, the temperature rose two to three days before biomarkers in blood samples changed. In animals receiving therapy, three weeks before creatinine and blood urea nitrogen increased.
Rejection can occur at any time after transplantation - immediately after surgery or years later. Often the process begins imperceptibly, and patients experience no symptoms in the early stages. If an immune reaction is detected in time, the doctor prescribes special therapy. If done too late, the organ will be lost, and the patient will find himself in a life-threatening situation.
Traditionally, biopsy and blood tests are used to diagnose rejection. But these tests cannot be done on a regular basis. Engineers believe that using regular monitoring will improve patients' quality of life and prevent the development of life-threatening symptoms. Scientists will continue testing the device on large animals before beginning clinical trials.