Ferrocene-phenylalanine hydrogels for immobilization of acetylcholinesterase and detection of chlorpyrifos

• Acetylcholinesterase was incorporated into the ferrocene-phenylalanine hydrogels.
• Acetylcholinesterase hydrolyzed acetylthiocholine to produce thiocholine.
• Ferrocene was an efficient redox mediator for the oxidation of thiocholine.
• Chlorpyrifos was detected by inhibition of the acetylcholinesterase activity.

We reported a new approach for the immobilization of acetylcholinesterase (AChE) on glass carbon electrode by employing ferrocene (Fc)-phenylalanine (denoted as Fc-F) hydrogels. To demonstrate the application of the modified electrode, chlorpyrifos, an AChE inhibitor, was determined. Specifically, with the addition of substrate acetylthiocholine, the enzymatic conversion from acetylthiocholine to thiocholine by AChE proceeded. The AChE/Fc-F modified electrode exhibited good electro-catalytic performance for the oxidation of the enzymatically produced thiocholine. In this process, the oxidized forms of Fc (Fc+) in the hydrogels were reduced by thiocholine, resulting in an increase in the anodic current of Fc. Based on the inhibition of the AChE activity, chlorpyrifos was determined with a detection limit of 3 nM. Analytical merits (e.g. stability, dynamic range, reproducibility, detection level, selectivity and regeneration) were also evaluated.