Characterization of binding of cholinesterases to surface immobilized ligands

We summarize here the development of various piezoelectric biosensors utilizing cholinesterase (ChE) as the recognition element. In our work we studied the interaction between cholinesterase and its ligands (propidium, carnitine, benzylgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) and paraoxon). The sensor modification was based on a self-assembled monolayer (SAM) of a thiol compound (11-mercaptoundecanoic acid) on the gold electrode and the subsequent covalent coupling of the cholinesterase ligand to this SAM. The ligand-modified piezoelectric sensors were placed in a flow system to allow the on-line monitoring of cholinesterase binding and the enzymatic activity quantification by amperometry. Cholinesterases from different species-acetylcholinesterase (AChE) from Electrophorus electricus , AChE from Drosophila melanogaster , and butyrylcholinesterase (BChE) of human origin-were tested on the various immobilized ligands. Our research allowed the development of a competitive assay for the detection of organophosphates in river water samples using the BZE-DADOO-modified piezosensor. Another direction of research was pointed on the characterization of the interactions between ChE and its ligands. The kinetic binding constants were derived using a one-to-one binding model.