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.