Microneedle-based electrochemical sensors for real-time pH and sodium monitoring in physiological environments

This study proposes developing microneedle (MN) sensors for pH and sodium detection. MNs are minimally invasive, miniaturized needles capable of piercing the stratum corneum to access dermal interstitial fluid (ISF). They can offer accessible, quick, and precise point-of-care diagnostics, potentially replacing centralized laboratory testing. The study uses electrochemical techniques for sensor modification, detection, and in-vitro characterizations. This work aimed to create and validate a polymer-based disposable microneedle patch for future transdermal electrochemical sensing. Successful potentiometric sensor development for pH detection using SiOx as passivation layers with IrOx functionalization was demonstrated. Additionally, voltametric sodium sensors were achieved with ARcare passivation and PEDOT functionalization. Both pH and Na⁺ sensors exhibited linear responses within normal physiological levels across various solutions. The pH sensors showed sensitivity of −60.5 mV/pH and an accuracy of 97.7 % alongside an error margin of 2.3 %, while sodium sensors achieved a sensitivity of 3.29 nA/mM/mm². Both sensors exhibit dynamic, rapid responses, along with good repeatability, stability, and selectivity. Over a twenty-one-day span for pH sensors and a fourteen-day period for sodium sensors, this study offers validation that microneedles serve as a viable foundation for wearable systems, enabling real-time, multiparameter biosensing of interstitial fluids.