Porous microneedle-based electrochemical sensor for potassium and glucose in skin interstitial fluid

The monitoring of biomarkers in interstitial fluid (ISF) holds significant promise for non-invasive, real-time health assessment. In this study, we present a novel porous microneedle-based electrochemical sensor (PMES) designed for the extraction and detection of key electrolytes and metabolites in ISF. The system integrates porous microneedles (PMNs) with screen-printed electrodes (SPEs) and polyethylene glycol (PEG)-loaded filter paper to facilitate efficient ISF collection and enable electrochemical detection. Both in vitro and in vivo experiments demonstrated the PMES's high biocompatibility and ability to detect potassium and glucose with reproducible, clinically relevant performance. For context, we also fabricated MN-electrode sensors (potentiometric Na⁺; amperometric glucose) and performed head-to-head comparisons, in which PMES exhibited superior long-term stability under identical insertion conditions. Compared with these directly functionalized MN electrodes prepared in this work, PMES maintained signal stability by decoupling ISF extraction (PMNs with PEG-assisted collection) from electrochemical transduction (external SPEs), thereby mitigating abrasion-induced coating delamination and biofouling; this comparison pertains to the architectures tested here and demonstrates the potential of PMES for minimally invasive, time-resolved health monitoring.