Development of new immunosensors for determination of contaminants in food

This article compares two different immunosensors developed for important food analytical and environmental problems. The label-free detection techniques were the piezoelectric quartz crystal microbalance measurement (QCM) and the optical waveguide lightmode spectroscopy (OWLS).Immobilizing anti-Escherichia coli IgG onto the gold electrode of QCM, E. coli bacterial cells were measured. Resonant frequency responses of the sensor system were determined at various concentrations of E. coli (1.7 × 105–8.7 × 107 CFU/ml). The same antibody was immobilized onto the amino silanized sensor of OWLS by glutaraldehyde covalent coupling. The measuring range was between 3 × 104 and 3 × 107 CFU/ml.Chloramphenicol (CAP) antibiotic was measured in standard solutions with immunosensor based on label-free techniques to study the possibility of direct sensing of molecules with low molecular weight. Anti-chloramphenicol antibody immobilization have been performed onto the gold surface of the crystal by using 3-mercaptopropionic acid (MPA) and dimethylaminopropyl-ethylcarbodiimide–hydroxysuccinimide ester (EDC-NHS) chemistry. The linear measuring range was found between 5 × 10−6 and 5 × 10−2 M chloramphenicol. Experiments were performed for measuring chloramphenicol with the same method with OWLS detection. After glutaraldehyde cross-linker immobilized the antibody, the signal measured was proportional to the analyte content in the range of 10−7–10−3 M.