Microneedle-Based Sensors for Wearable Diagnostics

Microneedles (MNs) are miniature medical devices, presented as an array of micro-scale needles, each under 1 mm in height with sharp tips. MN technology is becoming a diagnostic platform associated with several qualities: no pain and no risk of infection, offering accuracy, comfort, and usability. Monitoring biomarkers in interstitial fluid (ISF) in real time is crucial for tracking changes in metabolism and assisting in the early diagnosis of chronic illnesses. Some examples of MN sensors are summarized here: the real-time sensing of two metabolites (lactate and glucose or alcohol and glucose), the transdermal tracing of pH, Na+, K+, Ca2+, Li+, and Cl−, transdermal methotrexate (MTX) monitoring, the transdermal sensing of tyrosinase enzyme as a melanoma biomarker, the integration of CRISPR technology for nucleic acid analysis, and monitoring plant sap pH in the leaves of several plants. The challenges to be addressed to realize the transition to widespread One Health solutions are analyzed.