Electrochemical detection of peanuts at trace levels in foods using a magnetoimmunosensor for the allergenic protein Ara h 2

A highly sensitive disposable amperometric magnetoimmunosensor for the rapid determination of Ara h 2 protein, one of the major peanut allergens, is reported. The approach uses a sandwich configuration involving selective capture and detector antibodies and carboxylic acid-modified magnetic beads (HOOC-MBs). Detector antibodies are labeled with HRP-conjugated secondary antibodies and the MBs bearing the immunoconjugates are magnetically captured on surface of a disposable screen-printed carbon electrode (SPCE). The affinity reactions are monitored amperometrically at -0.20V (vs a Ag pseudo-reference electrode) in the presence of hydroquinone (HQ) as electron transfer mediator and upon addition of H2O2 as the enzyme substrate. The developed magnetoimmunosensor exhibits a wide range of linearity between 87 and 10,000pgmL-1 Ara h 2 with a detection limit of 26pgmL-1 as well as a great selectivity against other non-target proteins. The magnetoimmunosensing platform was successfully applied for the detection of Ara h 2 in different food extracts. After an appropriate sample dilution no matrix effects were observable. The developed methodology was able to detect trace amounts of the peanut allergen (0.0005% or 5.0mgkg-1) in wheat flour spiked samples. The results correlated properly with those provided by a commercial ELISA kit.