Diagnosis without injections
Researchers from the McKelvey School of Engineering at Washington University in St. Louis have developed a patch with microneedles that is glued to the skin and captures the biomarker of interest from the intercellular fluid. It has a high sensitivity, allowing clinicians to detect the presence of even a small amount of the substance being determined.
The clinic often draws blood to track biomarkers of the disease: antibodies that signal a viral or bacterial infection, or cytokines that indicate inflammation. But these biomarkers are not only present in the blood, they can also be detected in the intercellular environment.
Researchers have created a patch with microneedles, which, thanks to unprecedented sensitivity, allows clinicians to determine the presence of biomarkers in interstitial fluid.
No special skills are required for its use, the analysis can be performed at home by the patients themselves.
In addition to the low cost and ease of use, patches with microneedles have another advantage – unlike the traditional procedure of blood sampling, they are almost painless.
The principle of operation of a patch with microneedles is similar to a blood test, however, instead of using a solution to search for and quantify a biomarker in the blood, the microneedles directly capture it from the dermal interstitial fluid (interstitial fluid, ISF). After capture, biomarkers are qualitatively and quantitatively detected by fluorescence.
ISF is a rich source of various biomolecules, from neurotransmitters to cellular waste. Conventional biomarker analysis requires ISF extraction from the skin. This method is complicated, and usually the amount of ISF that can be obtained is not enough for analysis. This was a serious obstacle to the development of microneedle-based biosensor technology.
The new method involves the direct capture of biomarkers from the ISF without the need to extract the ISF itself. But the researchers faced a problem: it is very difficult to catch enough biomarker to detect it later using traditional analysis.
They used a "secret weapon" – the so-called plasmon fluores, which are ultra-bright fluorescent tags. Plasmon fluores enhance the signal of the target biomarker, making its glow about 1400 times brighter and allowing detection even at low concentrations. So, if earlier the concentration of a biomarker was supposed to be on the order of several micrograms per milliliter of liquid, then with the new patch, the research team was able to detect biomarkers in the amount of several picograms per milliliter – this is an order of magnitude more sensitive.
The new patch with microneedles will help track the level of antibodies in the body, which is especially important in a pandemic, because researchers working on vaccines against COVID–19 need to know whether the right antibodies are produced and how long they persist in the body. An easy-to-use patch will also be useful in emergency cases: for example, if a myocardial infarction is suspected, it will quickly determine the level of the specific biomarker troponin and allow you to choose the tactics of patient management. For people with chronic diseases requiring regular monitoring, patches with microneedles will help reduce the number of hospital visits, saving money, time and effort. In the laboratory, the use of this technology can limit the number of animals needed for studies in which several consecutive measurements are required to record the growth or decrease in the level of biomarkers.
The patches are practically painless, as they penetrate into the skin tissue by about 400 microns and do not even touch the nerve endings.
The authors still have a lot of work to do: it is necessary to determine the clinical thresholds, that is, the range of biomarkers in the ISF, which corresponds to the normal and pathological levels. The research team is also working on methods of delivering patches to remote regions with difficult climatic conditions.
Article Z.Wang et al. The Microneedle patch for the ultrasensitive quantification of protein biomarkers in interstitial fluid is published in the journal Nature Biomedical Engineering.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of Washington University in St. Louis: No more needles?