Diabetics are required to regularly monitor their blood glucose levels, conventionally via an invasive finger-prick blood test. Now, scientists at the University of Bath have created a non-invasive adhesive patch designed to measure glucose levels through the skin, potentially removing the need for this painful and unpopular procedure (Nature Nanotechnology doi: 10.1038/s41565-018-0112-4).
The patch does not pierce the skin, instead it samples glucose from interstitial fluid via extraction through hair follicles. The follicles are individually accessed via an array of miniature sensors using a small electric current. The glucose collects in tiny reservoirs and is measured every 10 to 15 minutes over several hours.
An important advantage of this device is that each sensor in the array can operate on a small area over an individual hair follicle, which significantly reduces inter- and intra-skin variability in glucose extraction and increases the measurement accuracy. As a result – and in contrast to other proposed non-invasive approaches, such as detection of glucose in sweat, tears or saliva – the patch does not require calibration with a blood sample.
“A needle-less method to monitor blood sugar has proven a difficult goal to attain,” explained Richard Guy. “The closest that has been achieved has required either at least a single-point calibration with a classic ‘finger-stick’, or the implantation of a pre-calibrated sensor via a single needle insertion. The monitor developed at Bath promises a truly calibration-free approach, an essential contribution in the fight to combat the ever-increasing global incidence of diabetes.”
In this study, Guy and colleagues tested the patch on pig skin, where they showed it could accurately track glucose levels across the range seen in diabetic human patients. They also tested it on healthy human volunteers, where again the patch was able to track blood sugar variations throughout the day.
They hope that the patch could eventually become a low-cost, wearable sensor that sends regular, clinically relevant glucose measurements to the wearer’s phone or smartwatch wirelessly, alerting them when they may need to take action.
“The specific architecture of our array permits calibration-free operation, and it has the further benefit of allowing realization with a variety of materials in combination,” explained Adelina Ilie. “We utilized graphene as one of the components as it brings important advantages: specifically, it is strong, conductive, flexible, and potentially low-cost and environmentally friendly. In addition, our design can be implemented using high-throughput fabrication techniques like screen printing, which we hope will ultimately support a disposable, widely affordable device.”
The next steps in this project – a collaboration between the University of Bath’s departments of physics, pharmacy and pharmacology, and chemistry – include refining the patch design to optimize the number of sensors in the array, demonstrating full functionality over a 24-hour wear period, and undertaking a number of key clinical trials.