In an effort to spare diabetics the pain and hassle of performing daily finger-prick blood glucose tests, various groups have developed continuous blood-sugar monitoring systems. Swedish scientists now believe that they may have improved on such technology, utilizing a skin patch that sports a tiny needle.

According to researchers at Stockholm's KTH Royal Institute of Technology, there are two main problems with today's continuous glucose monitoring systems (CGMS's). For one thing, because they incorporate a sampling needle that's at least 7 mm long, they can be uncomfortable. Additionally, that needle takes glucose measurements from within the fat tissue under the skin, which isn't ideal for obtaining the most accurate readings.

As a less painful and more precise alternative, the KTH team has developed an experimental skin patch, on the bottom of which is a silicon microneedle – it's just one-fiftieth the length of the needles used in conventional CGM systems.

Because it's so short, the microneedle protrudes only into the very top layer of the skin (less than 1 mm deep), where there are no nerve receptors. Natural capillary action causes the hollow needle to continually draw in interstitial fluid, which is the liquid that surrounds skin cells. An attached "extremely miniaturized" three-electrode enzymatic sensor is used to analyze that fluid, determining its (and thus the blood's) glucose content.

In lab tests, when placed on a volunteer's forearm, the patch was shown to be highly accurate at determining their glucose levels over an extended period of time. There was a delay of only about 10 minutes between the interstitial fluid being sampled, and readings being provided.

It is hoped that the technology could ultimately take the form of a reusable adhesive patch with integrated electronics. In the patch's current form, finger-prick tests would still have to be performed occasionally, in order to recalibrate the sensor (the same thing is true of existing CGSM's). Once the system is developed further, however, doing so may become unnecessary.

Other groups, incidentally, have been developing microneedle patches that could release insulin-regulating drugs into diabetics' bloodstreams as needed, eliminating the need for hypodermic injections.

A paper on the KTH research was recently published in the journal Biomedical Microdevices.