Microneedle Sampling and Analysis System for Painless Drug Monitoring

A microneedle sampling and analysis system was shown to accurately measure levels of the drug vancomycin in the interstitial fluid with results comparable to those obtained by classical blood testing.

Therapeutic drug monitoring typically requires blood drawn from patients in an uncomfortable and often painful fashion. An excellent example is monitoring of the drug vancomycin, which, due to the possibility of life-threatening toxic side effects, may require three to four blood draws per day.

As an alternative, investigators at the University of British Columbia (Vancouver, BC, Canada) and their colleagues at the Paul Scherrer Institut (Villigen, Switzerland) developed a painless and minimally invasive method using hollow microneedles to extract extremely small volumes (less than one nanoliter) of interstitial fluid to measure drug concentrations. This approach was justified by the fact that plasma and interstitial fluid are very similar. This similarity exists because water, ions, and small solutes are continuously exchanged between plasma and interstitial fluids across the walls of capillaries.

The new system consisted of a small, thin patch that was pressed against a patient's arm during medical treatment and measured the level of the drug painlessly without drawing any blood. The tiny needle-like projection was less than half a millimeter long, resembled a hollow cone, and did not pierce the skin like a standard hypodermic needle. The inner lumen of the microneedle was functionalized to be used as a micro-reactor during sample collection to trap and bind target drug candidates during extraction, without requirements of sample transfer. An optofluidic device was integrated with this microneedle to rapidly quantify drugs with high sensitivity using a straightforward absorbance scheme.

Vancomycin is currently detected by using volumes ranging between 50-100 microliters with a limit of detection of 1.35 micromoles. The microneedle-optofluidic biosensor system was shown to be capable of detecting vancomycin with a sample volume of 0.6 nanoliters and a limit of detection of less than 100 nanomoles.

"This is probably one of the smallest probe volumes ever recorded for a medically relevant analysis," said contributing author Dr. Urs Hafeli, associate professor of pharmaceutical sciences at the University of British Columbia.

"The combination of knowhow from the University of British Columbia and the Paul Scherrer Institut, bringing together microneedles, microfluidics, optics, and biotechnology, allowed us to create such a device capable of both collecting the fluid and performing the analysis in one device," said senior author Dr. Victor Cadarso, a research scientist at the Paul Scherrer Institut.

The microneedle technology is being commercialized by the spin-off company Microdermics Inc. (Vancouver, BC, Canada).

Details of the vancomycin sampling and analysis system were published in the July 6, 2016, online edition of the journal Scientific Reports.

Related Links:
University of British Columbia
Paul Scherrer Institut
Microdermics