Immunoenzymatic application of a redox potential biosensor

A silicon based potentiometric transducer (LAPS, Light Addressable Potentiometric Sensor) has been previously characterized both as a pH (Si3N4 sensitive surface) and as a redox potential sensor (metal sensitive surface). The transducer, in the redox configuration, has been used to monitor the enzymatic activity of HRP (Horse Radish Peroxidase) which can be used as a label in an immunoenzymatic application. A competitive immunoenzymatic assay for the detection of the pesticide 2,4-D (2,4-dichlorophenoxyacetic acid) has been set up. A monoclonal antibody has been immobilized both on a preactivated membrane and glass. The values of enzymatic activity measured by the sensor in these samples versus the analyte concentration show the typical trend of competitive immunoassays and the limit of detection is comparable to the one obtained with the conventional colorimetric methods (Enzyme Linked Immunosorbent Assay (ELISA)). These standard assays have been used as a check for our results and also as guidelines for the setting up of the experiments with the sensor.