Use of polyclonal antibodies to ochratoxin A with a quartz-crystal microbalance for developing real-time mycotoxin piezoelectric immunosensors

A piezoelectric immunosensor was tested for ochratoxin A (OTA) mycotoxin detection through the immobilization of OTA-bovine serum albumin (OTA-BSA) conjugate on gold-coated quartz crystals (AT-cut/5 MHz). Immunoassays were performed in a flow-injection system through frequency decreases in a quartz-crystal microbalance (QCM) because of a mass increasing during immunoreaction with anti-OTA antibodies. Three immobilization procedures for OTA-BSA (direct adsorption and covalent attachment to two alkane thiol self-assembled monolayers) were characterized with QCM in real time. Covalent attachment of the OTA-BSA conjugates through gold nanoparticles was also tested for amplifying the signal. Binding of the excess of antibodies to the immobilized OTA in an indirect competitive analysis decreased linearly the resonant frequency in the range of the OTA concentration from 10 to 128 ng/mL, with a detection limit of 8 ng/mL (signal/noise ratio of 3). A pepsin 2 mg/mL (pH = 2.1) solution was used to release antigen-antibody complexes, regenerating the biorecognition surface.