Electrochemical detection of organophosphorus pesticides based on amino acids conjugated nanoenzyme modified electrodes

In this work, amino acids (AAs) serine (S), histamine (H) and glutamic acid (E) attached nanoenzymes were found to help catalyze hydrolysis of organophosphorus pesticides (OPs) to form electroactive p-nitrophenol (PNP). This phenomenon follows the mechanism of proton transfer relay found in biomimetic hydrolases. So an electrochemical method using S, H, E conjugated TiO2 NPs (NPs) modified electrode to detect OPs was developed. TiO2 NPs were used as carriers and the attached AAs S, H, E have hydrolyzing activity toward hydrolysis of OPs, so the TiO2 NPs-AAs behave like nanoenzyme with hydrolysis activity. OPs (methyl paraoxon, methyl parathion and ethyl paraoxon) can produce electrochemical active PNP at this nanoenzyme modified electrode surface and OPs can be quantified via the electrochemical signals of PNP. This technique was selective toward OPs with p-nitrophenol group. The detection limit of methyl paraoxon, methyl parathion and ethyl paraoxon was about 0.2 mu M and the working range were two orders. Finally, this detection technique can be applied into the assay of OPs in real samples with high detection accuracy.