Potentiometric methods, cholinesterase

In AChE-based biosensors acetylthiocholine is commonly used as a substrate. The thiocholine produced during the catalytic reaction can be monitored using spectromet-ric, amperometric [44] (Fig. 2.2) or potentiometric methods. The enzyme activity is indirectly proportional to the pesticide concentration. La Rosa et al. [45] used 4-ami-nophenyl acetate as the enzyme substrate for a cholinesterase sensor for pesticide determination. This system allowed the determination of esterase activities via oxidation of the enzymatic product 4-aminophenol rather than the typical thiocholine. Sulfonylureas are reversible inhibitors of acetolactate synthase (ALS). By taking advantage of this inhibition mechanism ALS has been entrapped in photo cured polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ) to prepare an amperometric biosensor for... 

A huge number of methods based on enzyme inhibition-based biosensors can be found in the literature. Most times (57.6 %) acetylcholinesterase, butyrylchoU-nesterase, or cholinesterase are used followed by t3Tosinase (13 %) mainly combined with electrochemical procedures (44.5 % amperometric, 35.8 % potentiometric, frequently based on oxygen and pH measurements, and, to a very less extent, piezoelectrical). 

---