Doctors often use blood samples to check for biomarkers of disease such as antibodies or cytokines indicative of inflammation seen in conditions such as rheumatoid arthritis and sepsis.
These biomarkers are not just in blood — they can also be found in the dense liquid medium that surrounds cells but in a low abundance that makes it difficult to be detected.
Engineers have developed a microneedle patch that can be applied to the skin, capture a biomarker of interest, and thanks to its unprecedented sensitivity, allow clinicians to detect its presence. The technology is low-cost, easy for clinicians or patients themselves to use, and could eliminate the need for a trip to the hospital just for a blood draw. In addition, the microneedle patches have another advantage over blood draws: they are nearly pain-free.
Finding a biomarker using the microneedle patches is similar to blood testing but instead of using a solution to find and quantify the biomarker in blood, the microneedles directly capture it from the liquid that surrounds cells in the skin, which is called dermal interstitial fluid (ISF). Once the biomarkers have been captured, they’re detected in the same way: using fluorescence to indicate their presence and quantity.
ISF is a rich source of biomolecules, densely packed with everything from neurotransmitters to cellular waste; however, to analyze biomarkers in ISF, the conventional method generally requires extraction of ISF from skin. This method is difficult and usually the amount of ISF that can be obtained is not sufficient for analysis.
The microneedle patches use plasmonic-fluors, an ultrabright fluorescence nanolabel. Compared with traditional fluorescent labels, when an assay was done on a microneedle patch using plasmonic-fluor, the signal of target protein biomarkers shined about 1,400 times as bright and became detectable even when present at low concentrations.
These patches would allow providers to monitor biomarkers over time, particularly important when it comes to understanding how immunity plays out in new diseases. Researchers working on COVID-19 vaccines, for example, need to know if people are producing the right antibodies and for how long. The patch would indicate whether the person has antibodies against COVID-19 and at what level.
For people with chronic conditions that require regular monitoring, microneedle patches could eliminate unnecessary trips to the hospital, saving money, time, and discomfort.