Molecularly Imprinted Polymer-Based Electrogenerated Chemiluminescence Sensor for Sensitive and Selective Fentanyl Detection

The escalating prevalence of fentanyl, a highly potent synthetic opioid responsible for rising overdose fatalities and public health crises, underscores the critical need for sensitive and selective detection methodologies. Herein, we report a molecularly imprinted polymer (MIP)-based electrogenerated chemiluminescence (ECL) sensor for ultrasensitive and selective quantification of fentanyl. The sensor was fabricated by electropolymerizing 4-aminobenzoic acid (4-ABA) on a glassy carbon electrode (GCE) in the presence of fentanyl as the template, followed by template elution to yield recognition nanocavities within the MIP film. ECL signal transduction was achieved through the anodic coreactant pathway, wherein fentanyl (as the coreactant) bound within the MIP cavities reacted with solution-phase [Ru(bpy)₃]²⁺ (as the ECL emitter) in phosphate buffer (pH 7.5) during anodic scans from 0 to 1.60 V vs Ag/AgCl (3.0 M KCl). Critical fabrication and operational parameters, including electropolymerization cycles, template concentration and molar ratio to the monomer, elution conditions, and rebinding duration, were systematically optimized. Density functional theory and density of states investigations guided elution solvent selection and elucidated favorable fentanyl-polymer interactions, verifying the sensor's specificity toward fentanyl over five common structurally similar interferents. Under optimized conditions, the MIP-ECL sensor exhibited a limit of detection of ∼1 μM (S/N = 3), equivalent to 3.4 ng of fentanyl using 10 μL solution, with three distinctive linear regions spanning 1.0 to 6.0, 6.0 to 40.0, and 40.0 to 70.0 μM. Additionally, the sensor demonstrated high reproducibility and stability, positioning it as a promising platform for rapid forensic analysis of illicit fentanyl.