Development of Indirect-Competitive Optical Waveguide Lightmode Spectroscopy-based Immunosensor for Measuring Sulfamethazine

Sulfamethazine (SMZ) belonging to sulfonamide antibiotics is an important surveillance target because of its widespread presence in food materials and processed foods. In this study, a new detection on SMZ was conducted with an indirect-competitive optical waveguide lightmode spectroscopy-based immunosensor. As sensing element, the anti-SMZ antibody had good reactivity and specificity to SMZ-BSA as coating antigen. The sensor signals during the whole course of reaction comprising immobilization of the coating antigen and competitive immune reaction were stable enough to acquire reproducible results. The concentrations of the coating antigen and antibody selected for the immunosensing were 2 and 0.03129 mg/mL, respectively. When determined with 10-12-10-2 M SMZ, the limit of detection of the present sensor was presumed to be 1 pM. The coefficient of variability for five repetitive measurements using the same sensor chip was 5.41%. These results seemed to indicate that the immunosensor has a good potential to be used as a high-sensitivity analytical tool for SMZ in food matrices.