An Electrochemical Biosensor for Acrylamide Determination: Merits and Limitations

The present work reports the results concerning the development and implementation of the first electrochemical biosensor for acrylamide determination, based on a direct biochemical interaction between the analyte and intact bacterial cells, with intracellular enzymatic activity. The biological recognition element consisted of whole cells of Pseudomonas aeruginosa containing intracellular amidase activity, which catalyses the hydrolysis of acrylamide producing ammonium ion (NH4 + ) and acrylic acid. The transduction process was accomplished by means of an ammonium ion selective electrode. Whole cells were firstly immobilized on single discs of polymeric membranes, such as polyethersulphone, nylon and polycarbonate, which were, then, attached to the surface of the selective electrode. However, it was observed a significant loss of cells each time the biosensor was used, namely at the beginning of the assay, when the membranes were attached to the ammonium electrode, and after the assay, when removed for storage purposes. This evidence determined a premature decrease in the biosensor’s stability. Instead of using single membrane discs, a “sandwich” design, with two membrane discs was considered. This way the cells remain contained between the membranes, never contacting the electrode’s surface, preventing their premature loss. Consequently, the activity of the biosensor could be maintained for longer periods of time. The analytical performance of the biosensor was evaluated. The best results were obtained when polyethersulphone double membranes were used. A typical response of 120 mV (after 6 min reaction time), a Nernstian slope of 48 mV/decade, a limit of detection of 6.31×10 -4 M and a half-life time of 27 days, are examples of some