Lipase@ZIF-8 nanoparticles-based biosensor for direct and sensitive detection of methyl parathion

Organophosphorus pesticides especially p-nitrophenyl pesticides (methyl parathion) have neurotoxic effects and it is a difficult to remove organophosphorus pesticides residues from contaminated water. Present work has developed a sensitive, direct and rapid lipase@ZIF-8/chitosan/glassy carbon electrode (GCE) and lipase@amine-modified ZIF-8(An-ZIF-8)/chitosan/GCE biosensors for detection of methyl parathion. ZIF-8 and An-ZIF-8 nanoparticles which are a type of metal-organic frameworks with large surface area and high porosity have been facilely prepared under mild biocompatible conditions and used as lipase immobilization matrixes in the biosensors. The optimized lipase@ZIF-8/chitosan/GCE and lipase@An-ZIF-8/chitosan/GCE biosensors can detect methyl parathion with a wide linear range, good repeatability, recovery and limit of detection as low as 0.28 μM. The as-prepared biosensors can be stored in 0.05 M PBS (pH 7) at 4 °C and reused for at least 20 days with a retainment of at least 80% of its initial response to methyl parathion. This indicated that both ZIF-8/chitosan and An-ZIF-8/chitosan are suitable for immobilization of lipase that favors generation of p-nitrophenol from methyl parathion; and subsequent electrochemical oxidation and electron transfer of the p-nitrophenol.