Controlled immobilization of acetylcholinesterase on improved hydrophobic gold nanoparticle/Prussian blue modified surface for ultra-trace organophosphate pesticide detection

An ultrasensitive amperometric acetylcholinesterase (AChE) biosensor was fabricated by controlled immobilization of AChE on gold nanoparticles/poly(dimethyldiallylammonium chloride) protected Prussian blue (Au–PDDA–PB) nanocomposite modified electrode surface for the detection of organophorous pesticide. The Au–PDDA–PB membrane served as an excellent matrix for the immobilization of enzyme, which not only enhanced electron transfer but also possessed a relatively large surface area. In addition, the surface hydrophilicity of the Au–PDDA–PB nanocomposite was finely controlled in the static water contact angle range of 25.6–78.1° by adjusting the ratio of gold nanoparticles to PDDA–PB. On an optimized hydrophobic surface, the AChE adopts an orientation with both good activity and stability, which has been proven by electrochemical methods. Benefit from the advantages of the Au–PDDA–PB nanocomposite and the good activity and stability of AChE, the biosensor shows significantly improved sensitivity to monocrotophos, a typical highly toxic organophorous pesticide, with wide linear range (1.0–1000 pg/mL and 1.0–10 ng/mL) and an ultra-low detection limit of 0.8 pg/mL. The biosensor exhibits accuracy, good reproducibility and stability. This strategy may therefore provide useful information for the controlled immobilization of protein and the design of highly sensitive biosensors.