Electrochemical Biosensor Based on Polyelectrolyte Complexes with Dendrimer for the Determination of Reversible Inhibitors of Acetylcholinesterase

An acetylcholinesterase biosensor has been developed based upon a fourth generation poly(amidoamine) dendrimer with terminal amino groups. The immobilization of acetylcholinesterase was performed by physical adsorption onto the polyelectrolyte complex consisting of dendrimer and poly(styrene sulfonate) or deoxyribonucleic acid as counter ions. The efficiency of immobilization was evaluated by surface plasmon resonance that indicated a twofold increase of the quantity of enzyme on the surface in comparison with similar biosensors with no dendrimer. This property can be attributed to higher roughness of the underlying surface and its possible porosity caused by the star-shaped dendrimer molecules. The influence of the polyelectrolytes used on the biosensor performance as well as kinetic characteristics of enzymatic hydrolysis of thiocholine were assessed. The calibration curves of reversible inhibitors used in the therapy of neurodegenerative diseases (Huperzine A and galantamine) were ascribed with a four-parametrical logistic model. The 15% inhibition levels varied from 9.4 to 65 nM Huperzine A and 90 to 107 nM galantamine depending on the content of the polyelectrolyte complex. The biosensors were tested on example artificial and real urine samples and provided recoveries from 95 to 110%.