Analysis of cholinesterase binding to a carnitine-modified EQCM sensor

A sensor for cholinesterases (ChEs) has been developed by binding carnitine via 1,6-diaminohexane to a mixed monolayer of 11-mercaptoundecanoic acid/11-mercapto-1-undecanol on the surface of a gold-coated quartz crystal. Catalytically active and organophosphate-inhibited acetyl- and butyryl-cholinesterases of different origins were tested for their binding ability to d- and l-carnitine, respectively. The binding constants were calculated by using a one-to-one binding model. Additionally, the activity of the immobilized ChE was monitored and the operational stability was investigated amperometrically.