Microneedle biosensor (Imperial College London)
1 Oct. 2019. A clinical trial shows the feasibility of a patch worn on the skin to monitor a person’s antibiotic levels in real time, which the authors say can monitor other drugs. Medical and engineering researchers from Imperial College London in the U.K. describe the device and results in yesterday’s issue of The Lancet Digital Health.
The team led by Timothy Rawson, a research fellow at Imperial College, is seeking better tools to provide more personalized treatments of antibiotics and other drugs. Personalizing doses of antibiotics can reduce the chance of toxic overdose, since individuals often vary substantially in their reactions to some antibiotics, according to data cited by the authors. Also, antimicrobial resistance continues to be a major worldwide public health problem, and closer scrutiny of a patient’s need for antibiotics can help reduce their use in hospitals and clinics.
To monitor a patient’s antibiotic levels in real time, Rawson and colleagues developed a patch device worn on the forearm. The patch is made of polycarbonate, a transparent polymer often used in medical devices and instruments. The patch also contains sensor electrodes arrayed in microscale needles — where 1 micrometer equals 1 millionth of a meter — that intrude deep enough in the skin to contact blood vessels and tissue cells, yet not enough to cause pain. In addition, the patch has a thin layer of hydrogel, a water-based polymer, that absorbs extracellular fluid from tissue, where the sensors test for specific chemicals, as well as pH or acidic levels.
The early-stage clinical trial tested the patch with 10 healthy volunteers at Imperial College, seven of whom were male with an average age of 42. The patch worn by participants contained sensors measuring for beta-lactamase enzymes, indicating the presence of antibiotics in the extracellular fluid, as well as a patch with plain electrode needles for comparison and calibration. Both patches were wired to a data collection system. Participants also wore microdialysis devices, minimally invasive devices that measure chemical concentrations in tissue fluids, and gave 15 blood samples.
Trial participants were given five doses of penicillin, each 500 milligrams, every six hours — the standard dose for bacterial infections — starting the day before data collection. During the data collection period, participants were monitored in real time with the sensor patches, while extracellular fluid and blood samples were taken. No adverse effects were reported, with little discomfort noted from the microneedle patches.
The researchers compared the results from the microneedle patches to extracellular fluid analysis from the microdialysis devices. The findings show wide variations in beta-lactamase enzyme levels from one participant to the next, but readings from the microneedle patches largely agree with data from microdialysis, considered the gold standard for measuring composition of extracellular fluid, and blood samples.
The team says the results are promising enough to warrant a larger-scale clinical trial under more real-world conditions. Rawson notes in an Imperial College statement, “When patients in hospital are treated for severe bacterial infections the only way we have of seeing whether antibiotics we give them are working is to wait and see how they respond, and to take frequent blood samples to analyze levels of the drugs in their system ….” He adds, “By using a simple patch on the skin of the arm, or potentially at the site of infection, it could tell us how much of a drug is being used by the body and provide us with vital medical information, in real time.”
The researchers also note the technology can be applied to measuring concentrations of drugs other than antibiotics, and configured as part of closed loop systems, much like insulin pumps for people with diabetes, dispensing drugs in real time as needed by the individual patients.
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