Electrochemical biosensor based on polyelectrolyte complexes for the determination of reversible inhibitors of acetylcholinesterase.

Reversible inhibitors of acetylcholinesterase are increasingly applied in the Alzheimer's disease therapy. Their determination with biosensors requires special attention to the enzyme immobilization due to importance of electrostatic and steric factors affecting accessibility of the active site to the substrate and inhibitor present simultaneously. In this work, polyelectrolyte complexes have been assembled from electrochemically inactive components with implementation of acetylcholinesterase from electric eel. The influence of the complex components and enzyme position on the assembling efficiency was explored using surface plasmon resonance and kinetic parameters of the enzyme with amperometry with Co phtalocyanine mediator. The biosensor developed showed robust response toward donepezil and berberine with limit of detection of 0.46 and 70 nM, respectively, within 1 min after inhibitor addition. The sensitivity of determination coincides or is better than characteristics of biosensors based on covalently attached AChE described in the literature. The biosensor was tested on the example of drug determination in spiked samples of artificial urine (recovery 103% for 0.6 nM donepezil and 110% for 0.1 μM berberine).