Researchers say interstitial fluid could replace blood to monitor health and well-being — ScienceDaily

Researchers say interstitial fluid could replace blood to monitor health and well-being — ScienceDaily

The next frontier of continuous health monitoring may be skin deep.

Biomedical engineers at the University of Cincinnati say interstitial fluid, the watery fluid found between and around cells, tissues or organs in the body, could provide an excellent medium for early disease diagnosis or long-term health monitoring.

In a paper published in the journal Nature Biomedical Engineeringoutlined the potential technological advantages and challenges of using interstitial fluids.

“The reason we see it as a valuable diagnostic fluid is because of continuous access. With blood, you can’t easily take continuous readings,” said UC doctoral graduate Mark Friedel, co-lead author of the study.

“Can you imagine your day with a needle stuck in your vein all day? So we need other tools.”

Researchers are looking for other options to monitor a person’s health and well-being. Sweat is a good measure of certain things like stress or anxiety because it contains hormones like cortisol. But the body is stingy with other chemicals that are not so easily released in sweat, said Friedel.

“Sweat glands are great filters that don’t let everything through,” he said. “So more than half of the things we want to monitor don’t have access to any sweat.”

Blood is the gold standard for health monitoring. But humans also have a liter of interstitial fluid that makes up 15% of their body weight.

“The main feature of blood that makes it so advantageous is that we understand blood very well,” Friedel said. “If there is something in your blood, we know what will happen to your heart or your liver,” he said.

Researchers said interstitial fluid has many of the same chemicals in the same proportions as blood, offering an alternative to expensive and time-consuming lab work.

The study outlined the different ways doctors can sample interstitial fluid, from applying suction to the skin to using microdialysis.

“As biomedical engineers, one of our biggest goals is to help people better manage their health by making diagnostics more accessible,” said co-lead author Ian Thompson at Stanford University.

“A major obstacle to this accessibility is that most current diagnostics rely on blood sampling, which can be painful and requires trained personnel to perform. Therefore, in recent years there has been an increasing interest in using interstitial fluid just under the skin as a diagnostic sample. which is more accessible and less painful.”

In UC’s College of Engineering and Applied Science, students are developing sensors to measure hormones and other chemicals in interstitial fluid. They use microneedles less than 1 millimeter long that pierce the skin through a tiny patch.

“If you had a splinter, it probably went deeper into your skin than our microneedles,” Friedel said. “They’re usually painless. Most of the time I don’t feel it. The most uncomfortable part is removing the tape that holds the device down.”

But even if you don’t know it’s there, your body does, Friedel said. And this minute reaction can affect the results of the test.

“There is a Schrödinger observer effect with interstitial fluid. Whenever you try to collect it and measure it, you inherently change the fluid itself,” Friedel said. “If you stick a needle in your skin, your body becomes inflamed and then your body [sample] levels vary. For continuous biomonitoring, we want to know those concentrations as they are when you’re not getting a small needle.

“That’s why it’s such a challenging fluid that hasn’t been used outside of diabetes monitoring.”

Still, the researchers say, interstitial fluid holds enormous promise for monitoring health through wearable technology. This could help doctors track the effectiveness of drugs to ensure proper dosage or provide early diagnosis of illness by monitoring the immune system.

But Friedel said there is still much to learn.

“We are trying to unlock the box and read the instructions inside to understand what is in interstitial fluid and what are the possibilities to exploit it,” he said.

Friedel and Thompson worked with co-author Heikenfeld, UC’s James L. Winkle College of Pharmacy, Sandia National Laboratories in New Mexico and Southeast Missouri State University.

The study was funded by grants from the National Science Foundation, the US Air Force Office of Scientific Research and the US Office of Naval Research.

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