SMALL-VOLUME ONLINE SENSOR FOR CONTINUOUS MEASUREMENT OF GAMMA-AMINOBUTYRIC-ACID

We report the first on-line electrochemical sensor for the continuous measurement of gamma-aminobutyric acid (GABA), which is a well-known i nhibitory neurotransmitter in the nervous system. The sensor is compos ed of a glutamate oxidase (GluOx) and catalase immobilized small-volum e enzymatic reactor and a glassy carbon (GC) electrode modified with a top layer film consisting of gabase and GluOx coimmobilized bovine se rum albumin and an Os-poly(vinylpyrridine) bottom layer film containin g horseradish peroxidase. The response of the sensor depends on the a- ketoglutarate concentration and is almost saturated when its concentra tion is 100 times higher than GABA, The sensor exhibits a sensitivity of 1.56 nA/mu M for GABA under optimized conditions and shows almost n o response when 10 mu M glutamate is continuously injected. A detectio n limit of 0.1 mu M is obtained with a linear range of 0.1-10 mu M. GA BA can be measured in the absence of alpha-ketoglutarate when there is L-glutamate in the sample solution, which is a typical condition for the extracellular measurement of cultured nerve cells.