Detection of cadmium in water through laboratory designed enzyme inhibition-based bio-electrochemical system

The work presents designing of an enzyme inhibition-based bio-electrochemical system for the detection of cadmium (Cd) in water. The electrode is fabricated by coating a thin layer of graphene oxide on indium tin oxide (ITO) coated glass substrate and subsequent chemical immobilization of alkaline phosphatase (ALP) enzyme using bovine serum albumin and glutaraldehyde. Different experimental parameters are investigated and optimized to quantify the inhibition of the catalytic activity of the ALP in the presence of Cd. ALP catalytic activity is determined by the voltammetric determination of the electroactive product p-nitrophenol formed after the enzymatic reaction with p-nitrophenyl phosphate which is used as substrate. The cyclic voltammetry showed that under optimized conditions p-nitrophenol could be oxidized electrochemically on the ALP/GO/ITO electrode at around +1.04 V. Optimized incubation time for the signal measurement is found to be 30 min and the relative inhibition of enzyme activity at 10 ppm concentrations of Cd²⁺ is found to be 34%.