Acetylcholinesterase biosensor based on assembly of multiwall carbon nanotubes onto liposome bioreactors for detection of organophosphates pesticides

Abstract

A novel acetylcholinesterase (AChE) biosensor based on multilayer films containing multiwall carbon nanotubes (MWCNTs), chitosan (CS) and AChE liposomes bioreactor (ALB) was developed. ALB were prepared by encapsulating the enzyme AChE in l-α-phosphatidylcholine liposomes resulting in spherical bioreactor with a mean diameter of 7.3±0.85μm. Porins were embedded into the lipid membrane, allowing for the free substrate transport, but not that of the enzyme due to size limitations. The glassy carbon electrode (GCE) was alternately immersed in MWCNTs, CS and ALB solution to assemble different layers of multilayer films [(MWCNTs/ALB)n/GCE]. Among the resulting biosensors, the biosensor based on six bilayers of multilayer films was best. The properties of the resulting biosensor were measured by electrochemical measurements. Based on the inhibition of organophosphate pesticides on the AChE activity, using dichlorvos as a model compound, the inhibition of dichlorvos was proportional to its concentration ranging from 0.25 to 1.75μM and from 2.00 to 10.00μM, with a detection limit of 0.68±0.076μg/L estimated at a signal-to-noise ratio of 3. The apparent Michalis–Menten constant, Km, for the enzymatic reaction was 0.28mM. The fabrication of the biosensor was simple, the response was fast and the stability was acceptable. The novel biosensor has many potential applications, the foremost being in detection of organophosphorus pesticides.