Tissue fluid surrounds the cells of the body, it comes out of the small blood vessels. This fluid is needed to transfer nutrients to tissues and remove metabolic products from them. From the intercellular space, fluid enters the lymphatic capillaries and returns to the blood.
The authors of the new study indicate that interstitial fluid contains biomarkers that can be used in diagnosis. However, it is not used for this purpose, since there are no available methods for its collection.
American scientists have developed a microneedle patch that makes small holes in the skin and can collect tissue fluid for analysis. Previously, such attempts were unsuccessful, because an admixture of blood got into the liquid. The authors of the new study were able to tackle this problem.
In the study, scientists collected tissue fluid from 21 people. They compared her test results with her blood test results. Tissue fluid and blood samples had similar levels of many clinically important substances, including glucose, caffeine, and vitamin D.
Microneedles are much smaller than conventional needles and leave very small holes in the skin that can tighten throughout the day. Scientists emphasize that blood clots do not form in interstitial fluid, unlike blood, so such a patch would be convenient to use for long-term monitoring of the level of some bimarkers in the body. Currently, there is a technique for long-term monitoring of blood glucose levels, but it requires the introduction of a subcutaneous sensor.