Micro-droplet hydrodynamic voltammetry for the determination of microcystin-LR based on protein phosphatase

Microcystin-LR (MC-LR) is one of the most frequent and most lethal toxicants and a vital environmental pollutant due to its toxicity and persistence. It is hepatotoxins and have been shown to be potent tumor-promoters which pose a serious threat to human health in the form of chronic exposure through drinking water. In this study, a novel electrochemical method for the determination of MC-LR has been developed using protein phosphatase 2A (PP2A) enzyme inhibition. The rapid and simple determination of PP2A activity was accomplished by means of hydrodynamic voltammetry in a 50 μL micro-droplet with a rotating disk electrode (RDE). The chronoamperometric response were obtained from the electrochemical oxidation of p-aminophenol (PAP) following the enzymatic conversion of p-aminophenyl phosphate (PAPP) as a substrate. PP2A activity estimated by using PAPP substrate is affected by MC-LR, and this phenomenon decreases the current signal of PAP. The IC₅₀ value was calculated as 0.08 μg/L which is well below the World Health Organization (WHO) provisional guideline value for total MC-LR of 1 μg/L in drinking water. The enzymatic reaction using RDE is possible to perform using fewer chemicals in a rapid manner. Therefore, the method can be very attractive for MC contaminated drinking water routine assessment.