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Microneedle System Designed for Drug Monitoring

Microneedle array

Microneedle drug-monitoring array (University of British Columbia)

25 July 2016. Researchers in Canada and Switzerland designed a device that measures drug concentrations in patients with tiny microneedles on the skin rather than frequent invasive blood tests. The team from University of British Columbia in Vancouver and Paul Scherrer Institute in Villigen, Switzerland described their prototype system earlier this month in the journal Scientific Reports.

The research team is seeking a more practical and less painful method to monitor in patients concentrations of drugs like the antibiotic vancomycin. This anti-bacterial drug is given in cases of serious infections, when few if any options are available, and must be closely monitored to maintain effective concentrations. But vancomycin must also be watched to avoid giving too large a dose, which can lead to serious side effects including kidney failure and deafness.

Tracking vancomycin levels with today’s commercial testing kits require taking blood samples as often as 3 or 4 times a day. In addition to discomfort to the patient, the tests and their separate lab analysis add considerable costs. Thus a point-of-care therapeutic drug monitoring device would both benefit the patient and likely reduce cost of care to the payers.

The solution devised in the labs of UBC pharmaceutical sciences professor Urs Häfeli, engineering professor Boris Stoeber, and researcher Victor Cadarso at Paul Scherrer Institute builds on advances showing a high correlation between drug concentrations in interstitial fluid and blood serum. Interstitial fluid is found in the spaces between cells and makes up much of the fluid content in the body, and samples of that fluid can be drawn from just beneath the outer layers of skin.

Their device is a collections of tiny hollow needles, less than half a millimeter in length, mounted on a base of polydimethylsiloxane or PDMS, a biocompatible silicone polymer used in breast implants and other medical applications. The insides of the microneedles are lined with peptides known to bind to vancomycin. The reaction of these peptides to the presence of vancomycin is then detected with a laser signal and optical fibers running through the PDMS base, and sent via a waveguide — a form of electronic channel — to a photodetector device.

The microneedles pierce barely below the outer skin and absorb a minute amount of interstitial fluid, 0.6 nanoliters, for testing, thus causing no discomfort for the patients, according to the authors. In simulated lab tests, the researchers found the device could take a stable reading in less than 5 minutes. In addition, the system was sensitive enough to track varying levels of vancomycin in test samples.

Häfeli and Stoeber, with first author Sahan Ranamukhaarachchi, are co-founders of Microdermics, a 2-year-old start-up enterprise in Vancouver, commercializing the technology. The company plans to apply the technology, however, to drug delivery, as an alternative to traditional hypodermic needle-based drug injections, and is aiming for early-stage clinical trials in 2017. Häfeli serves as Microdermics’ chief scientist, Stoeber as its chief technologist, and Ranamukhaarachchi as vice-president for R&D.

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