Amperometric detection of the herbicide mesotrione based on competitive reactions at nitroreductase@layered double hydroxide bioelectrode

A mesotrione monitoring biosensor was prepared using a nitroreductase (NfrA2) immobilized on a glassy carbon electrode by adsorption on nanoparticles of Mg2Al-NO3 layered double hydroxides (MgAl-NPs). The amperometric transduction process was based on a competitive enzymatic reduction between Fe(CN)(6)(3-) and mesotrione, both substrates of NfrA2. Indeed in the presence of the NADH cofactor, Fe(CN)(6)(3-) was enzymatically reduced and the Fe(CN)(6)(4-) released was then oxidized at the electrode. When mesotrione was added to the electrolyte solution, a competitive enzymatic reaction took place at the NfrA2@MgAl-NPs modified electrode leading to a decrease of the electrocatalytic anodic current. Mesotrione can thus be detected by chronoamperometry at 0.375 V/SCE with a sensitivity of 18.4 mA M-1 cm(-2) over a linear concentration range between 5 and 60 mu M (R-2 = 0.998) and a detection limit (3 sigma) of 3 mu M.