Covalent fabrication of methyl parathion hydrolase on gold nanoparticles modified carbon substrates for designing a methyl parathion biosensor

• AuNPs can be fabricated to the GC surfaces by Au–C bonding.
• A novel biosensor based on the covalent attachment of methyl parathion hydrolase on AuNP modified GC substrates is presented.
• The fabricated biosensor can be used for direct detection of methyl parathion with high sensitivity, stability, specificity and reproducibility.
• The AuNP modified sensing interface is potential for on-site detection of a spectrum of pesticides or small molecules.

A biosensor based on AuNP modified GC electrodes has been developed for direct detection of methyl parathion. AuNP can be introduced to mixed monolayers of aryldiazonium salt modified GC electrodes by Au–C bonding through aryldiazonium salt chemistry, which provides a stable interface showing efficient electron transfer between biomolecules and electrodes. PEG molecules were introduced to the interface to resist non-specific protein adsorption. AuNP surfaces were further modified with 4-carboxyphenyl followed by covalent immobilization of methyl parathion hydrolase (MPH), a specific biocatalytic enzyme to methyl parathion. Exposure of this interface to methyl parathion resulted in a change in amperometric signal due to the MPH catalytic hydrolysis of methyl parathion producing electroactive compound 4-nitrophenol. This biosensor shows high selectivity, specificity, reproducibility and stability, and is functional for the detection of methyl parathion in real samples. The linear range for detection of methyl parathion is 0.2–100 ppb with a detection limit of 0.07 ppb in 0.1 M phosphate buffer at pH 7.0.