'Band aid' burns to check transplant organ health

2019-03-02 08:10:00

By Phil McKenna A patch that monitors the health of organs awaiting transplant by burning into their surface could offer simpler organ health checks to surgeons. The patch would provide continuous updates on the status of kidneys and other organs more easily than repeatedly taking samples, as clinicians must do today. Constantly monitoring the health of an organ is crucial prior to transplant surgery, since it may be without a blood supply for several days. Currently, medical staff use large needles to withdraw tissue fluid for lab analysis, a process that can itself put strain on the organ if done repeatedly. “It’s very difficult to keep organs in a viable state from the time they are harvested until they are transported and transplanted,” says James Castracane of the University at Albany in New York. “There is strong need for more continual, less invasive monitoring.” Castracane and colleagues created a small, flat device about 2.5 centimetres square with 25 micro-heaters embedded. When placed on the outside of an organ like a small Band aid, these heaters burn small holes – one fifth the width of a human hair – into the outermost layer of the organ. “We’re doing this on a micro scale – if it was done on your skin you wouldn’t even feel [those holes],” says Anand Gadre also at Albany. Roughly one micro-litre of tissue fluid then oozes out of each hole, onto an electrochemical sensor inside the patch. This sensor detects either glucose or lactate levels within the fluid, based on how well the fluid conducts electricity when mixed with different enzymes. The levels of those two products of different metabolic reactions can be used to judge the overall metabolic rate or health of the organ. “We would know the baseline of these readings and then [compare] in real time to see if the organ is in a viable state or not,” says Gadre. Each micro-burner can only penetrate the organ’s outer layer once. But a patch with a large number of these burners, say 100s, could monitor the organ as many times as it had heaters. So far, the patch’s electrochemical sensors have been tested in a laboratory setting. The group now plans to fix a number of patches on the outside of kidneys harvested from cows. “It sounds like an interesting approach and early evidence seems promising, but only time will tell,” says Robert Gabbay of Penn State University in Hershey, Pennsylvania. Gabbay says, if the patch works, it might also be used by diabetic patients to continually measure glucose levels in their blood. Several companies have developed interstitial glucose sensors that provide continuous monitoring, but they have to be embedded underneath the skin, via a catheter. But the ultimate sensor would be one that can continuously monitor the level of glucose in the blood, not in tissue fluid. “Interstitial glucose is always a little off from blood glucose, especially when it changes rapidly,” says Gabbay. “The big step forward will be to look at blood glucose non-invasively.” A paper on the transplant organ monitoring patch was presented at the Materials Research Society 2008 Spring Meeting, San Francisco,