Transdermal Creatinine Sensing in Live Animals with an Integrated Electrochemical Microneedle Patch

Over 700 million people worldwide are estimated to suffer from chronic kidney disease (CKD), and creatinine is a critical biomarker for diagnosing and managing CKD. However, conventional detection relies on invasive blood sampling and time-consuming protocols and is susceptible to interference from endogenous substances and drugs. This highlights an urgent demand for convenient, non-invasive, and accurate monitoring strategies. This study presents a wearable electrochemical microneedle (MN) patch for minimally invasive and enzyme-free creatinine detection in transdermal interstitial fluid (ISF). Solid polycarbonate MNs are coated with conductive poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate). Copper ions (Cu2+) are immobilized on the surface through immersion treatment via coordination and electrostatic interactions, and a Nafion film is finally deposited to enhance stability and anti-interference ability. Quantitative detection is based on the peak current generated from the electrochemical oxidation of in situ formed Cu0 to Cu+, which subsequently undergoes specific coordination with creatinine. The patch exhibits a linear detection range of 5.00-300 μM for creatinine with a minimum detectable concentration of 1.00 μM. Benefiting from the strong coordination effect and permselectivity of Nafion, the patch shows high stability, excellent anti-interference ability, and reliable sensing performance. Integrated with a handheld potentiostat, this compact, lightweight, and low-cost sensor achieves real-time and accurate creatinine sensing within 90 s in ISF of live rabbit models, showing great promise for long-term home-based CKD management.