A biosensor for Escherichia coli based on a potentiometric alternating biosensing (PAB) transducer

In the present paper, we describe a biosensor for the detection of bacterial contamination in drinking water based on an immunoassay test. The biological component was made by a rabbit polyclonal antibody obtained utilising an environmental strain of Escherichia coli, DH5α. This strain, showed a capsular protein pattern typical of this species. Cells present in water samples were detected by a complete potentiometric alternating biosensor (PAB). The PAB system consists of a measuring chamber, acquisition and driving electronics and the appropriate software: the apparatus is computer controlled in order to obtain on-line acquisitions and recording of data. The transducer principle is based on a light addressable potentiometric sensor (LAPS) technology which, in our case, reveals the production of NH3 by a urease–E. coli antibody conjugate. The proposed system appears to be very sensitive and fast, in comparison with conventional methods: concentrations of 10 cells per ml were detected in an assay time of ca. 1.5 h. No signals were detected from other potential water polluting bacteria, such as Pseudomonas marina and Sphaerotilus natans and also from bacteria such as Klebsiella oxytoca phyletically related to E. coli.