Direct electrochemical sensing of ampicillin in milk using a screen-printed electrode modified with conductive molecularly imprinted polymer-coated gold nanoparticles

The synergistic effect of gold nanoparticles (AuNPs) incorporated into molecularly imprinted over-oxidized poly(ethylenedioxythiophene) (MIP-OPEDOT) films to enhance the electrochemical detection of ampicillin has been investigated. The MIP-OPEDOT films were electropolymerized cyclically on a screen-printed carbon electrode in the presence of ampicillin as the template molecule. After template removal, the resulting cavities enabled selective rebinding of ampicillin, modulating charge transfer at the electrode surface and generating a measurable electrochemical signal. The sensor was characterized using physicochemical (FTIR, AFM, SEM/EDS) and electrochemical (cyclic voltammetry, electrochemical impedance spectroscopy) techniques. Square-wave voltammetry revealed a wide linear detection range (1–750 pg mL⁻¹), an ultralow detection limit (1.8 pg mL⁻¹), and a low quantification limit (5.94 pg mL⁻¹). The sensor exhibited exceptional selectivity against structurally similar molecules, high stability and good reproducibility. Validation in real milk samples demonstrated its applicability in agri-food analysis, with recoveries of 110–118%, underscoring its potential for food safety and environmental monitoring.

Graphical Abstract