Enzymatic recycling for signal amplification: Improving microcystin detection with biosensors

A novel strategy for the electrochemical signal amplification based on enzymatic recycling is presented. p-Aminophenyl phosphate was chosen as enzyme substrate and diaphorase and NADH oxidase as amplifying enzymes. Bioelectrocatalysis was observed by cyclic voltammetry using alkaline phosphatase as a model enzyme. Chronoamperometry experiments with diaphorase resulted in an amplification factor of 26.8. The amplification system was applied to the microcystin detection with a protein phosphatase 2A inhibition-based biosensor. The amplification enlarged the linear range by more than four orders of magnitude and decreased the limit of detection from 37.75 to 0.05 μg/L, making the biosensor useful as a reliable screening tool to assess the quality of water.