Hate needles? Well, have we got good news for you. In an attempt to combat our reliance on needles for diagnostic testing, engineers from the McKelvey School of Engineering at Washington University in St. Louis have created a microneedle patch that is attached to the skin and can detect trace amounts of disease biomarkers with extreme sensitivity, replacing the lengthy process of blood draws. Studded with tiny microneedles, the patches may look sinister but are supposedly "pain-free", and can even be used by the patient without supervision in the comfort of their own home. Their research was published in the journal Nature Biomedical Engineering. Many diseases can be diagnosed through the detection of proteins that circulate in the blood – whether that be as a consequence of the disease, such as inflammatory markers that may highlight the presence of autoimmune disorders, or molecules that directly cause diseases, such as from pathogens or drugs. These biomarkers provide a rapid method for diagnosis and testing, but current techniques require invasive and expensive procedures of blood drawing and lab testing before results can be received. Instead, the patches utilize another source of these biomarkers – the dermal interstitial fluid (ISF). This fluid exists between blood vessels and cells, containing nutrients and a variety of important molecules needed for all the cellular processes in the body, and making up around 26% of the body’s water. Reaching the dermal ISF is easy, requiring a tiny puncture just below the skin surface. “They go about 400 microns deep into the dermal tissue,” Professor Srikanth Singamaneni, whose lab developed the microneedle patches, said in a statement. “They don’t even touch sensory nerves.” To tap into this incredible diagnostic resource, the microneedle patch needs to be extremely sensitive. Although the ISF is rich in biomarkers, difficulty drawing enough from the body for reliable testing has previously made them not viable for clinical use. So, the engineers employed tiny fluorescent labels that glow in the presence of the target biomarkers, called plasmonic-fluors. These nanoprobes have exploded in popularity amongst researchers recently, owing to their incredible sensitivity that is nearly 800 times the sensitivity of conventional fluorescent markers. Alongside that, plasmonic-fluors were markedly faster, allowing them to be utilized in a patch for a quick test. When used on mice for a variety of different biomarkers, the patches were effective at testing, whilst not suffering the drawbacks of tissue destruction and patient disturbance that repeated blood sampling has. The researchers now hope the patches, with more testing, could be used in clinical settings for either constant biomarker monitoring, such as COVID-19 testing (which plasmonic-fluors have shown incredible promise in already), or instant diagnostics in emergency rooms. “When someone complains of chest pain and they are being taken to the hospital in an ambulance, we’re hoping right then and there, the patch can be applied,” said Jingyi Luan, one of the lead authors of the paper. For now, the patches must be validated for a variety of conditions, and undergo rigorous clinical trials before they can be approved. The current study is a proof-of-concept in mice, and many biomarkers will need to be verified for direct links to disease before the patches will be of use. Source
