Label-free electrochemical DNA biosensor for detection of peanut allergen Ara h2 based on gold nanoparticles-modified self-assembled monolayers in food matrices

A label-free electrochemical genosensor for the detection of Ara h2, a major peanut allergen, has been developed using mixed self-assembled monolayers (SAMs) for DNA immobilization. The study used a sandwich format and compared gold nanoparticles-modified screen printed carbon electrodes (AuNPs-SPCE) and screen printed gold electrodes to obtain a highly sensitive bioplatform. Different binary and ternary SAMs were evaluated as sensing phase, by electrochemical impedance spectroscopy and cyclic voltammetry, obtained the best signal to noise ratio with CP-DTT-AuNPs-SPCE. The genosensor demonstrated a linear response in the concentration range of 0.025–10 nM, with a detection limit of 0.02 nM by square wave voltammetry. The precision of the biosensor was validated, showing a RSD of less than 8 % across different concentrations. Selectivity tests confirmed negligible signals for non-complementary sequences. Additionally, the method proved effective in real food matrices, with recovery rates between 95.0 % and 105.5 % in spiked soy-based beverage and low-fat cow's milk. • Label-free genosensor for Ara h2 using binary mixed SAMs. • AuNPs–SPCE provided a highly sensitive electrochemical bioplatform. • Wide dynamic range (0.025–10 nM) with detection limit of 0.02 nM. • Excellent reproducibility (RSD < 8 %) and high sequence specificity. • Recovery of 95–106 % in spiked foods, supporting food safety monitoring.