The fluid in between your cells could help reveal health problems - New Scientist

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Size comparison of a microneedle patch used to extract interstitial fluid versus a hypodermic needle used to obtain blood samples. — A microneedle patch used to extract interstitial fluid (left) and a needle used to obtain blood samples (right)

The fluid between our cells could be used to diagnose and monitor health conditions. A patch made from tiny needles can sample this fluid and could be easier to use and less invasive than normal blood tests.

Interstitial fluid, also known as tissue fluid, is the fluid which surrounds all our cells. This liquid leaks out of our blood vessels and into our body’s cells to deliver essential nutrients, while simultaneously removing waste products.

“The fluid that fills the spaces between cells in tissues makes up almost a quarter of our bodily fluids,” says Mark Prausnitz at Georgia Institute of Technology.

Prausnitz and his colleagues developed a patch made of five stainless steel microneedles that can create small punctures in a person’s skin. The researchers tested the patch on 21 people by using it to take small amounts interstitial fluid out of the body and comparing it to blood samples.

The team found similar levels of important compounds in both samples – including glucose, caffeine and vitamin D. The researchers say this means that the approach could be used to test for these compounds and diagnose health problems related to their levels, such as diabetes. As the needles in the patch are much smaller than normal needles, the skin can heal from the punctures within a day.

Previous methods used to draw interstitial fluid out of the body struggle with contamination from blood. To combat this, Prausnitz and his team gently ramped up the suction pressure used by the patch to leave any nearby blood vessels unruptured.

“[This approach] may be more acceptable than blood tests – especially in paediatric medicine,” says Timothy Miles Rawson at Imperial College London. Additionally, it could be used for continuous monitoring, as interstitial fluid does not clot, he says.

Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aaw0285