Description:

Chemically selective ultramicroelectrodes form the backbone of the resource technology and the support of our user group and BioCurrents has made several technical improvements in their design and manufacturing. Broadly these electrodes can be divided into potentiometric, based on ion selective liquid membranes, and amperometric, based on redox chemistry at a metal or carbon interface. Enzyme assisted electrodes are dealt with in a separate project. Whereas the development of the potentiometric sensor has made significant progress towards a simple disposable ion selective microelectrode, the same cannot be said of the amperometric variety. This is a solid-state sensor design based on a metal (gold, platinum) or carbon core. The final tip diameters are approximately 4 microns. Construction has been tedious, time consuming, with a variable final product. There are no commercial sources for these sensors. To date the BRC has developed, to application, basic amperometric sensors for oxygen, nitric oxide, ascorbate and hydrogen peroxide. The same bodies are used for enzyme assisted, which cover glucose, glutamate and lactate. Improving the efficiency of fabrication of the solid-state microelectrodes is an ongoing project.

Progress:

This reporting year has seen considerable progress in the rate and reliability of amperometric microelectrode designs. Several technical improvements have occurred. Firstly, electrodes are now fabricated in batches of five with parallel processing through the etch and calibration procedures. Secondly, it was observed that the etching process of the metal core could be achieved in sodium hydroxide alone making the use of potassium cyanide unnecessary. This is an important step in the projected automation of the process. An exceedingly important development has been the successful and repeatable insertion of the cellulose acetate membrane on the tips of the oxygen electrodes. This imparts the required diffusion limitation that enhances the electrode performance. With these developments our current electrodes designs have better performance criteria both in repeatability and application performance. Lastly, we have achieved the goal of reducing the overall cost of production to less than $50.