Polymer Nanozymes: Electropolymerized Enzyme Mimics for the Detection of Oxidative Stress Biomarkers.

3-Nitro-l-tyrosine (NO₂Tyr) serves as a critical biomarker of oxidative stress, closely linked to the pathogenesis of neurodegenerative and inflammatory disorders. This study presents a highly sensitive and selective nonenzymatic electrochemical sensor that uses polymer nanozyme properties for the detection of NO₂Tyr in human saliva. The sensor design integrates molecularly imprinted poly(3-aminophenol) (MIP) films, electropolymerized directly onto graphitic electrodes (GPE) via cyclic voltammetry (CV), with NO₂Tyr acting as the molecular template. By mimicking enzyme-substrate recognition, the MIP/GPE sensor exhibits superior electrochemical performance without relying on biological enzymes. Surface analysis confirms uniform MIP film formation, while electrochemical characterization reveals a significant reduction in charge transfer resistance and enhanced electroactive surface area, facilitating rapid electron transfer critical for sensitive NO₂Tyr detection. Sensor measurements reveal a linear detection range of 0-1000 nM, a low limit of detection (LOD) of 0.21 nM, and a sensitivity of 0.94 μA cm^-2 nM^-1 toward NO₂Tyr. The sensor maintains high selectivity against common salivary interferents, including structurally similar l-tyrosine (Tyr), and achieves an overall 95.9% recovery rate in different human saliva samples. This MIP-based sensing platform introduces an effective enzyme-mimetic strategy for selective NO₂Tyr recognition, offering a robust, disposable, and cost-efficient tool for point-of-care (PoC) monitoring of oxidative stress biomarkers. Its operational simplicity, stability, and compatibility with complex biological fluids position it as a promising candidate for early stage screening and management of oxidative stress-associated neurodegenerative diseases.