O. Niwa et al., Continuous monitoring of L-glutamate released from cultured rat nerve cells with a microfabricated on-line sensor at a slow flow rate, ELECTROANAL, 11(5), 1999, pp. 356-361
A microfabricated online L-glutamate sensor was developed to monitor change
s in the local concentration of L-glutamate released from cultured nerve ce
lls. The sensor consists of two glass plates and a fused silica sampling ca
pillary. One of the glass plates has rectanglar flow channels cut into it w
ith a dicing saw and the other has three carbon film based electrodes. One
of the electrodes was modified with an Os-polyvinylpyrridine-based polymer
layer containing horseradish peroxidase. A GluOx enzyme layer was immobiliz
ed upstream of the working electrode. A syringe pump in the suction mode wa
s used to sample extracellular fluid continuously via a glass capillary wit
h a pointed end. The sensor sensitivity did not decrease with decreasing fl
ow rate when the Bow rate was reduced to about 200 nL/min. This is because
the increase in the conversion efficiency compensated for the decrease in t
he analyte flow into the sensor. As a result, a low detection limit (6.4 nM
) was obtained at a slow flow rate. In an in vitro experiment, the extracel
lular fluid near a particular nerve cell was sampled through a capillary an
d continuously introduced into the sensor via the suction provided by a syr
inge pump. The nerve cells were stimulated by KCl and a transient L-glutama
te release with a sharp peak was monitored with a slow Bow rate of 500 nL/m
in to 2 mu L/min.