Grants and Contracts Details
Description
This proposal is a renewal application of a grant that was funded to develop ceramicbased
multisite microelectrodes for electrochemical and electrophysiological recordings. The
development of ceramic-based multisite microelectrodes represents a parallel technology to the
use of semiconductor-based microelectrodes. During the previous 3-year funding period we
have successfully designed a multi-layer thin film microelectrode that has 4 Platinum recording
sites that are insulated from the substrate, connecting lines and the bonding pads with
polyimide. The resulting microelectrodes are cut out from a 1 cm x 1 cm ceramic wafer using a
computer-controlled diamond saw. Yield is 64 per wafer with a success rate of 95%. The
resulting microelectrodes have a triangular shape, 1 cm length, 2-5 micron tip and range from
37 to 125 microns in thickness. Two major designs were explored during the previous funding
period: serial 4-site arrays and side-by-side microelectrode pairs. However, we have assembled
over 9 different designs, to investigate optimization of the recording site properties. The current
designs have been configured to record glutamate, choline, acetylcholine and gammaaminobutyric
acid (GABA), using a Nafion layer coupled with a layer of oxidase enzyme, which
is formed with glutaraldehyde and bovine serum albumin. In vitro and in vivo studies in
anaesthetized animals support that the microelectrodes are capable of recording rapid changes
in glutamate and choline using a new self-referencing recording paradigm. In addition, soak
tests and in vivo electrophysiological recordings support that the microelectrodes can last up to
30 days in vivo. This is the first demonstration of microelectrode arrays formed from ceramic
substrates and our papers and progress report support that these microelectrodes may be
useful for a variety of neurochemical and electrophysiological applications.
The present application concerns the more complete development of reliable ceramicbased
microelectrode arrays for electrochemical recordings of neurotransmitters in CNS tissues.
There are several issues that need to be resolved in order to use these microelectrodes for
rapid, selective and sensitive recordings of glutamate, choline, acetylcholine and GABA in vivo.
First, while the microelectrodes are sensitive and useful when incorporating our "self-referencing
recording procedures", the microelectrodes can record interferents such as dopamine and
norepinephrine. We will use two major strategies, the use of electrodeposited polyphenylenediamine
films (with Dr. Robert O'Neill) and the use of an oxidase-enzyme based
redox polymer (with Dr. Adrian Michael) to further improve the selectivity of the microelectrodes.
Second, with the help of PCB Assembly, a local microelectronics engineering and
manufacturing company, we will develop a micro-connector system to improve the performance
of the microelectrodes and decrease production cost. Third, we are developing a low cost microcoater
system, for more reliable micro-application of the enzyme layers to the microelectrodes.
This is needed to allow for the use of the technology in other laboratories. Fourth, we will
investigate micro-nanostructure formation (with Dr. Todd Hastings) to further reduce the
microelectrode size, but try to attain sensitivities that rival larger microelectrode arrays. This is
an exciting area for microelectrode development. By reducing the size of the recording sites, we
may further enhance sensitivity, response time and packing density of the arrays. This may
contribute to a more detailed understanding of the brain. Finally, we will pursue the development
of the recording technologies in awake behaving rats. This is an important step in allowing the
linkage between behavior and the neurochemical changes that occur during brain function. All
of our proposed experiments should contribute to improved performance of the microelectrode
arrays for chemical recordings in vivo. These technology improvements should decrease the
cost of these sensors and associated devices, so that they can be used by other scientists.
Such technology, may contribute to a better understanding of the dynamics of glutamate,
choline, acetylcholine and GABA signaling in the brain and spinal cord.
Status | Finished |
---|---|
Effective start/end date | 7/1/04 → 6/30/08 |
Funding
- National Science Foundation: $800,817.00
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