Fluorescent microneedle patches detect biomarkers at much lower levels
Nobody likes needles – at best they’re an unpleasant means to an important end. Microneedle patches could be a painless alternative, and now researchers have developed a way to use them to detect biomarkers at much lower levels, without drawing blood.
Microneedle patches are emerging as a less invasive way to deliver drugs or monitor someone’s health. As the name suggests, they’re made up of a sticky patch that can be applied to the skin like a Band-Aid, pressing an array of tiny little needles into the top layer of skin. These microneedles are too small to reach nerve receptors, making them basically painless.
They are however big enough to get to the interstitial fluid, the medium that surrounds our cells. That lets them deliver drugs to treat things like diabetes or skin cancer, administer vaccines and contraception, detect disease or monitor the changing levels of glucose or antibiotics in a patient’s system.
The problem is, biomarkers are often much harder to detect in interstitial fluid than in blood. So, for the new study, researchers at Washington University in St Louis found a way to boost the signal. The team developed a new kind of ultra-bright fluorescent tag called plasmonic-fluor, which glows some 1,400 times brighter than current tags in response to a given biomarker.
That means that the system can detect much lower levels of the biomarkers. Where previous tags detect biomarkers at concentrations of a few micrograms per milliliter of fluid, the plasmonic-fluor can find them at just picograms per ml – a millionth of the concentration.
In tests in mice, the researchers used the microneedle patches and the new tag to look for a protein called periostin. Sure enough, the new setup improved the detection limit by almost 800 times.
This newfound sensitivity could make microneedle patches more viable for longer-term monitoring of chronic conditions in patients, or to keep an eye on how treatments are progressing. But of course there’s still plenty of work to do, with the team noting that in particular they need to figure out just what constitutes normal or abnormal levels of biomarkers in interstitial fluid.
The research was published in the journal Nature Biomedical Engineering.