2002 Volume 51 Issue 12 Pages 1121-1133
The present paper describes analytical aspects of electrochemical ultramicrosensors constructed using glass capillaries having a tip diameter of 0.5∼12 μm. The constructed sensors included open capillary electrodes with the sampling ability of analytes based on electrokinetic phenomena and capillarity, membrane sensors in combination with planar bilayer lipid membranes (BLMs) and excised biomembrane sensors. The open capillary sensor had abilities of electrokinetic sampling and charge-selective detection of analyte ions. Selective detection of dopamine in a neutral solution after being transported into an inner acidic solution of the open capillary sensor was also demonstrated. The constructed capillary membrane sensors include (i) a novel sensor that mimics the mode of signal transduction displayed by G protein-linked receptors with BLMs containing receptors and a single gramicidin channel, (ii) an excised biomembrane sensor that allows the detection of arachidonic acid selectively over its metabolites and other fatty acids, and (iii) L-glutamate sensors using BLMs and biomembranes containing a glutamate receptor. The response characteristics of these capillary sensors were studied in terms of the working principle, dynamic range, sensitivity and selectivity. The application of these sensors to detection of signaling molecules in mouse brain slices was also demonstrated.
