Flow-Through Acetylcholinesterase Sensor with Replaceable Enzyme Reactor

Fast and reliable determination of enzyme inhibitors are of great importance in environmental monitoring and biomedicine because of the high biological activity and toxicity of such species and the necessity of their reliable assessment in many media. In this work, a flow-through biosensor has been developed and produced by 3D printing from poly(lactic acid). Acetylcholinesterase from an electric eel was immobilized on the inner walls of the reactor cell. The concentration of thiocholine formed in enzymatic hydrolysis of the substrate was monitored amperometrically with a screen-printed carbon electrode modified with carbon black particles, pillar[5]arene, electropolymerized Methylene blue and thionine. In the presence of thiocholine, the cathodic current at −0.25 V decreased because of an alternative chemical reaction of the macrocycle. The conditions of enzyme immobilization and signal measurements were optimized and the performance of the biosensor was assessed in the determination of reversible (donepezil, berberine) and irreversible (carbofuran) inhibitors. In the optimal conditions, the flow-through biosensor made it possible to determine 1.0 nM–1.0 μM donepezil, 1.0 μM–1.0 mM berberine and 10 nM to 0.1 μM carbofuran. The AChE biosensor was tested on spiked samples of artificial urine for drugs and peanuts for carbofuran. Possible interference of the sample components was eliminated by dilution of the samples with phosphate buffer. Easy mounting, low cost of replaceable parts of the cell and satisfactory analytical and metrological characteristics made the biosensor a promising future application as a point-of-care or point-of-demand device outside of a chemical laboratory.

Efficient Preservation of Acetylcholinesterase at Room Temperature for Facile Detection of Organophosphorus Pesticide

A simple and inexpensive strategy is reported to facilitate the detection of an organophosphorus pesticide by acetylcholinesterase (AChE). Pullulan is able to preserve AChE at room temperature, but the activity of conserved AChE varies significantly depending on the time, stir and volume of solution to dissolve it. The reason is that AChE entrapped in pullulan tablet remains in an inactive state to avoid denaturalization and deactivation. There is a reactivation process to gradually recover the enzyme activity during dissolution of the tablet. Stirring would interrupt this procedure and lead to a loss of enzyme activity. Dissolution of the tablet for 5 min with a volume of 15 μL could facilitate full recovery of AChE activity. The feasibility of activated AChE for organophosphorus pesticide detection was evaluated using malaoxon. These results contribute to the understanding of preservation mechanism by pullulan and the development of easy-to-use enzyme assays.