Label-Free Amperometric Magnetoimmunosensors for Direct Determination of Lactoperoxidase in Milk

Novel label free electrochemical magnetoimmunosensors for the determination of lactoperoxidase (LPO) were developed based on the use of streptavidin-magnetic beads (Strep-MBs) and graphite-Teflon composite or screen-printed carbon electrodes (SPCEs) as electrochemical transducers. Biotinylated antiLPO antibodies were immobilized onto the Strep-MBs and a direct-type immunoassay by detecting the enzymatic activity of the captured target enzyme using amperometric detection at −0.20 V and the H2O2/hydroquinone (HQ) system was employed. The SPCEs-based magnetoimmunosensors allowed a detection limit (LOD) of 0.12 μg mL−1 and a good selectivity against nontarget proteins. Moreover, their analytical usefulness was successfully demonstrated by analyzing different types of milk samples.