A robust Pt nanozyme for visual isoniazid determination in commercial tablets and biosamples

A reliable method for isoniazid (INH) determination is critical for personalized tuberculosis therapy. In this study, we developed a robust colorimetric biosensor using a peroxidase (POD)-like platinum nanozyme (Pt-NZ) as the signal transducer. Pt-NZ features simple preparation, batch-to-batch reproducibility, and catalytic efficiency comparable to those of other Pt-based nanozymes. Mechanistic investigations confirmed that ˙OH dominates the H₂O₂ decomposition, supported by both experimental evidence and density functional theory (DFT) calculations. The biosensor exhibits a broad linear range of 5-35 µM, with a limit of detection (LOD) of 1.46 µM and a limit of quantification (LOQ) of 4.57 µM. It shows acceptable selectivity against common interferents in various sample matrices. Validation in artificial urine samples demonstrated good agreement with high-performance liquid chromatography (HPLC), and spike-and-recovery tests in commercial tablets, urine, and serum yielded satisfactory results. This work establishes a proof-of-concept for a practical Pt-NZ-based colorimetric assay for INH, supporting therapeutic drug monitoring and pharmacokinetic studies.