When people are in the early stages of an undiagnosed disease, immediate tests that lead to treatment are the best first steps. But a blood draw—usually performed by a medical professional armed with an uncomfortably large needle—might not be quickest, least painful or most effective method, according to new research.
Now a technique using microneedles able to draw relatively large amounts of interstitial fluid—a liquid that lurks just under the skin—opens new possibilities. Previously, microneedles—tiny, hollow, stainless steel needles—have drained tiny amounts of interstitial fluid needed to analyze electrolyte levels but could not draw enough fluid to make more complicated medical tests practical. The new method’s larger draws could be more effective in rapidly measuring exposure to chemical and biological warfare agents as well as diagnosing cancer and other diseases, says Sandia National Laboratories researcher and team lead Ronen Polsky, who is principal investigator on the project sponsored by the Defense Threat Reduction Agency and Sandia’s Laboratory Directed Research and Development program.
“We believe interstitial fluid has tremendous diagnostic potential, but there has been a problem with gathering sufficient quantities for clinical analysis,” said Polsky. “Dermal interstitial fluid, because of its important regulatory functions in the body, actually carries more immune cells than blood, so it might even predict the onset of some diseases more quickly than other methods.”
Polsky, along with the University of New Mexico, the U.S. Army Edgewood Chemical Biological Center and other Sandia researchers described the new technique in an Oct. 22 paper in the Nature journal Communications Biology.
The relatively large quantities of pure interstitial fluid extracted, which have never before been achieved, make it possible to create a database of testable molecules, such as proteins, nucleotides, small molecules and other cell-to-cell signaling vesicles called exosomes. Their presence or absence in a patient’s interstitial fluid would then indicate, when an individual’s data is transmitted by electronic means to a future data center, whether bodily disorders like cancers, liver disease or other problems might be afoot.
The new microneedle extraction protocol achieved its latest results by modifying a technique described in a 1999 technical paper. The original technique drew fluid with a microneedle attached to a flat substrate penetrating the skin. In the recent modification, a concentric ring from a horizontally sliced insulin pen injector surrounding the needle was used serendipitously and a far greater amount of fluid became available.