Analysis of intercellular fluid
Biochemical information about the body most often comes from a blood test, which is only 6% of the body's fluid. But valuable information can also be extracted from the analysis of other biological fluids, which are usually difficult to collect. A new study has developed a way to produce interstitial fluid that circulates between cells. For this purpose, the method of minimally invasive insertion into the skin was used. Interstitial fluid analysis can provide information about cell metabolism products, diagnostic biomarkers, and will allow evaluating potential toxins absorbed through the skin. Since interstitial fluid does not clot like blood, extraction with a microneedle patch may offer a new approach for continuous monitoring of glucose levels and other important health indicators.
Interstitial fluid is formed in the blood, and then enters the tissues through the capillaries to deliver nutrients to the cells. The researchers suggested that since interstitial fluid is in direct contact with cells, it should carry more information about tissues than blood.
The idea of interstitial fluid analysis is not new: there are already tools for monitoring glucose in it, and previously other researchers used surgically implanted tubes and vacuum-created papules to take samples through the skin, but these methods are not suitable for routine clinical diagnosis.
Researchers from the Georgia Institute of Technology and Emory University used a patch with five rigid stainless steel microneedles, the length of which is one-fourth of a millimeter.
The patch was applied to the skin of 50 volunteers. He created micropores that reached only to the outer layer of the skin containing interstitial fluid, which was collected using an aspirator. As a result, a sufficient amount of interstitial fluid was obtained from each participant to perform three types of analysis. For control, blood samples were taken from the same participants and interstitial fluid was obtained using an older vacuum papule method.
The researchers needed to avoid getting blood into the interstitial fluid. There are no large blood vessels in the outer layers of the skin, but microneedles can touch capillaries. During the experiments, the researchers found that if the aspiration after the introduction of microneedles is increased slowly, it is possible to obtain a liquid that does not contain blood.
The procedure of extraction of interstitial fluid took about 20 minutes for each subject. The volunteers underwent the procedure well, the microscopic pores healed during the day with minimal irritation.
The extracted liquid was analyzed at Emory University using liquid chromatography and mass spectrometry methods to determine the chemicals contained in it. In total, about 10,000 unique compounds were found, most of which were also found in blood samples. However, about 12% of the chemicals were not detected in the blood, and others were contained in interstitial fluid in higher concentrations than in the blood.
Although not all compounds unique to interstitial fluid could be analyzed, the research team identified components of care products that are applied to the skin, such as hand lotions and pesticides that can enter the body through the skin. Thus, the new microneedle technique may be useful in dermatological and toxicological studies to determine whether certain substances accumulate in the skin over time. We are talking about materials that can be stored in the tissues of our body, but are not found in the bloodstream.
Using interstitial fluid, the researchers also determined the pharmacokinetics of caffeine and the pharmacodynamics of glucose, demonstrating that this method can also carry information about biomarkers in dynamics. Researchers have found a strong correlation between blood glucose levels and interstitial fluid, so a microneedle-based system can provide a less invasive alternative to existing implantable glucose sensors, allowing sensitive components to remain on the skin surface.
In future studies, the authors plan to reduce the time required to extract interstitial fluid and simplify the process by abandoning the aspiration pump. In addition, the search for compounds found in the liquid that have medical diagnostic value will continue.
Article by Pradnya P. Samant et al. Sampling interstitial fluid for human skin using a microneedle patch is published in the journal Science Translational Medicine.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru Based on Georgia Tech: Extraction of Largely Unexplored Body Fluid May Provide New Biomarkers.