An amperometric enzyme-linked immunosensor for Nitrobacter

A new amperometric enzyme-linked immunoassay for specific enumeration of Ni trobacter has been developed. This assay uses an electrode made of glassy c arbon, on which the immunological reaction is carried out. The method is ba sed on a competitive immunoassay principle, utilising monoclonal primary an tibody and alkaline-phosphatase-labelled secondary antibody. The enzyme sub strate 5-bromo-4-chloro-3-indolyl phosphate generates an electroactive prod uct which is amperometrically detected. The effects of different parameters on the performance of the sensor have been studied. Quantitative detection of Nitrobacter using the immunosensor has been compared to a previously de veloped enzyme-linked immunosorbent assay showing compatible results. In ad dition, the overall assay time can be shortened with this new sensor. A det ection limit of approximately 3 x 10(6) Nitrobacter cells/ml was obtained.