On-Line Flow Sensor for Measuring Acetylcholine Combined with Microdialysis Sampling Probe

We have developed an on-line electrochemical sensor for the continuous measurement of acetylcholine (ACh). The sensor comprises a small volume prereactor containing immobilized choline oxidase (ChOx) and catalase (or horseradish peroxidase, HRP), a small volume enzymatic reactor containing immobilized acetylcholine esterase (AChE) and ChOx and a glassy carbon electrode modified with Os-polyvinylpyrridine -HRP. The sensor can measure ACh selectively even when the choline (Ch) concentration is more than 1000 times that of ACh, when the ChOx and catalase are immobilized in the prereactor. The sensor shows a wide linear relationship from 5 nM to 1 μM and a detection limit of 5 nM (S/N = 2), which is comparable to the ACh detection limit achieved by liquid chromatography/electrochemistry. It also shows high selectivity against other neurotransmitters and interferents. The properties of the sensor combined with a microdialysis (MD) probe were also studied by measuring a solution containing a much higher concentration of Ch than ACh.