Small-volume on-line 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 inhibitory neurotransmitter in the nervous system. The sensor is composed of a glutamate oxidase (GluOx) and catalase immobilized small-volume enzymatic reactor and a glassy carbon (GC) electrode modified with a top layer film consisting of gabase and GluOx coimmobilized bovine serum albumin and an Ospoly(vinylpyrridine) bottom layer film containing horseradish peroxidase. The response of the sensor depends on the alpha-ketoglutarate concentration and is almost saturated when its concentration is 100 times higher than GABA. The sensor exhibits a sensitivity of 1.56 nA/microM for GABA under optimized conditions and shows almost no response when 10 microM glutamate is continuously injected. A detection limit of 0.1 microM is obtained with a linear range of 0.1-10 microM. GABA 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.
Niwa
O
O
NTT Basic Research Laboratories, Kanagawa, Japan.
Kurita
R
R
Horiuchi
T
T
Torimitsu
K
K
D000818:Animals; D015374:Biosensing Techniques; D002374:Catalase; D002417:Cattle; D004800:Enzymes, Immobilized; D009862:Online Systems; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D004800:Enzymes, Immobilized; D005680:gamma-Aminobutyric Acid; D002374:Catalase