A Microneedle-Based Electrochemical Sensor with Multiplex Detection in Physiological Environment and Incorporated in a Portable Device

The number of disorders linked to deficiencies in vital ions, such as calcium (Ca²⁺) and potassium (K⁺), has dramatically increased in recent years. Numerous research studies have proposed the development of a sensor for early detection; however, the bulk of these investigations include the time-consuming process of drawing blood samples for testing. To overcome these challenges, this research highlights the development of a novel portable microneedle-based device for the multiplexed detection of Ca²⁺ and K⁺, as well as pH, in artificial interstitial fluid (ISF). A passivation layer of ArCare was investigated to improve the stability, reliability, and repeatability of the microneedle sensors, enhancing their sensitivity and accuracy. Microneedle sensors were modified with Poly-(3,4-ethylenedioxythiophene) (PEDOT) and an ion-selective membrane (ISM) to reduce interference caused by other ions when tested in complex media. Successful modification of the surface with PEDOT and ISM was confirmed using electrochemical characterization, Raman Spectroscopy, and Scanning Electron Microscopy (SEM) analysis. The results demonstrated a linear response in the detection of both Ca²⁺and K⁺ ions with respect to concentration, with a high coefficient of determination (<i>r</i> ² >0.9) indicating strong reliability. Additionally, tests were carried out to study the effect of pH on the detection of Ca²⁺ and K⁺, revealing a linear detection for both ions across varying pH levels. The multiparametric detection of pH and Ca²⁺ or K⁺ was carried out using an in-house built smart sensing platform known as Portable Unit Lab-on-Site Electrochemistry (PULSE). Overall, this work highlights the potential of multi-ion microneedle sensors in portable real-time health monitoring applications.