We've heard about microneedle patches before, and we've also heard about cheap, disposable paper biomedical testing kits. Japanese scientists have now combined the two, in a paper-backed microneedle patch that measures blood glucose levels.
Typically, microneedle patches consist of a small polymer square, the underside of which is studded with an array of tiny needles.
When such a patch is pressed against the body, the needles painlessly pierce the top layer of skin. Those needles then draw in the interstitial fluid that surrounds the skin cells, so it can be analyzed. Because biomarker levels in that fluid typically correspond to those in the bloodstream, microneedle patches can often be used instead of the more painful hypodermic needles that draw actual blood samples.
For the experimental new device, a team at the University of Tokyo started by pouring a mixture of melted biodegradable polymer and salt into a mold which incorporated tiny cone-shaped cavities – these formed the microneedles. The mold was then flipped over needle-side-up, and the polymer layer's flat back was pressed down against a sheet of paper. This caused the polymer to flow into the pores of the paper, bonding with it.
After the polymer/paper combo was removed from the mold, its microneedles were cooled in a solution that drew out the salt. This left the needles filled with thousands of tiny pores, which draw in fluid via capillary action. Finally, using double-sided tape, a piece of glucose-sensitive paper was attached to the base paper.
When the resulting patches were tested on an agarose gel containing dissolved glucose, the pores in the needles successfully drew in fluid which travelled up through the base paper and into the glucose-sensing paper. This caused the latter to change color, indicating the amount of glucose present in the gel.
It is now hoped that once the microneedle patches are developed further, customers could use the cheap, disposable, biodegradable and biocompatible devices in their own home, to test themselves for prediabetes. That said, the technology could reportedly be adapted to test for various other conditions, by implementing paper that's sensitive to biomarkers other than glucose.
The research is described in a paper that was recently published in the journal Medical Devices & Sensors.
Source: University of Tokyo