A Scalable Paper‐Based Electrochemical Sensor Employing MWCNTs for Isoniazid Detection

Isoniazid (INZ) is an antimicrobial agent that treats tuberculosis by inhibiting the InhA enzyme in Mycobacterium tuberculosis, making sensitive and reliable methods for routine monitoring essential to ensure safe and effective therapy. We report the development of a novel paper‐based electrochemical sensor for the sensitive and selective detection of isoniazid. The sensor is constructed using a gold inkjet‐printed electrode (GIPE) modified with gold nanoparticles (AuNPs), chitosan (CH), and multi‐walled carbon nanotubes (MWCNTs), forming a GIPE/AuNPs/CH/MWCNTs sensor. Electrochemical deposition of AuNPs effectively addressed insulating gaps generated during the sintering of the gold ink, enhancing electrical conductivity and surface uniformity. The synergistic combination of AuNPs and MWCNTs increased the electroactive surface area and improved electron transfer kinetics, while chitosan provided excellent film‐forming ability, stability, and biocompatibility. The resulting sensor demonstrated excellent analytical performance for INZ, offering a broad linear detection range of 1 – 100 µm and achieving low detection limits of 0.31 µm in PBS and 0.29 µm in urine. Additionally, it demonstrated high selectivity, reproducibility, and stability, highlighting its potential as a simple, cost‐effective, and high‐performance platform for INZ detection in pharmaceutical and clinical applications.