Microneedle Patch With Fluorescent Nanolabels Detects Antibodies In Skin

Researchers at the Washington University in St. Louis have developed a microneedle patch that can help to detect small amounts of antibodies in interstitial fluid. The painless technology could provide an alternative to blood draws for antibody tests, such as those used in the COVID-19 response. The new technology overcomes a bottleneck with many microneedle patch systems – their poor sensitivity. The researchers used “plasmonic-fluors,” fluorescent nanolabels, to detect protein biomarkers present in small amounts in interstitial fluid.

Blood draws are the go-to method for diagnostic testing, but they can be painful and inconvenient. Microneedle patches, where a patch studded with tiny needles is applied to the skin to obtain a sample of the interstitial fluid that resides between our cells, offer an easy and painless alternative.

However, protein biomarkers, such as antibodies, are typically present in low concentrations in interstitial fluid, making it difficult to detect them in microneedle-derived samples. To date, this has been a bottleneck for microneedle technology.

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This new system uses plasmonic-fluors to boost the detection of proteins present at very low levels. The signal from the target biomarkers in samples was approximately 1,400 times brighter than that from conventional fluorescent labels.

“Previously, concentrations of a biomarker had to be on the order of a few micrograms per milliliter of fluid,” said Zheyu (Ryan) Wang, a researcher involved in the study in the announcement. The new system can detect biomarkers at the picograms per milliliter range. “That’s orders of magnitude more sensitive,” added Ryan.

In a nice bonus, the patches are essentially pain-free. “They are entirely pain-free. They go about 400 microns deep into the dermal tissue,” said Srikanth Singamaneni, another researcher involved in the study. “They don’t even touch sensory nerves.”

So, how might the patches be used? They may be effective in determining immune responses to COVID-19 vaccines, for example. “Let’s put a patch on, and let’s see whether the person has antibodies against COVID-19 and at what level,” added Singamaneni.

Soure