Pulsed galvanostatic control of a solid-contact ion-selective electrode for potentiometric biosensing of microcystin-LR

We report here on the development of a chronopotentiometric assay for microcystin-LR based on enzymatic inhibition. The inhibition of protein phosphatase by microcystin-LR can be sensed potentiometrically by using 4-nitrophenyl phosphate as an enzyme substrate. A solid-contact ion-selective electrode (ISE) with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) as a transduction layer has been designed for potentiometric biosensing using the pulsed galvanastatic technique. By applying an anodic current, the enzymatic generated p-nitrophenol can be extracted into the polymeric membrane with tetradodecylammonium tetrakis(4-chlorophenyl)-borate to produce the chronopotentiometric signal. Meanwhile, a controlled voltage was applied to refresh the membrane for multiple consecutive measurements. The proposed potentiometric assay showed a linear response for microcystin-LR in the range 1-100 mu g/L with a detection limit of 0.5 mu g/L (3 sigma). We believe that the proposed method can be employed for sensitive, rapid and reliable determination of analytes involved in enzyme inhibition. (C) 2016 Elsevier B.V. All rights reserved.