This application describes a systematic program of research aimed at the development of micron-sized sensors for the measurement of neurotransmitter release and uptake in """"""""real-time"""""""" using biotin/avidin technology. The objective of this work is to perform submicrometer-sized modification of the surface through generation of oxidized regions of carbon for use as covalent bonding sites for further modification. Direct attachment of functional molecules is also proposed. Experiments with oxidative modification are aimed towards generating microscopic regions with a specific type and density of surface oxide to provide a constructed surface that is optimized for use as a sensor device. Spatially-localized modification of carbon fiber electrodes is proposed on the sub-micron scale to allow spatial segregation of enzyme-binding sites from electron transfer sites. Specifically, photocleavable reagents can be used to locally protect/deprotect derivatization sites on carbon electrode surfaces to allow spatial segregation of enzyme attachment sites from redox sites. The use of photolithographic techniques will produce sub- micron segregation of redox and enzyme sites. Latex nanoparticles (30 - 200 nm dia.) will serve as sites of attachment for redox enzymes to increase the surface loading of the enzyme without interfering with electron-transfer sites on the electrode. Fluorescence microscopy with high resolution will be employed to characterize the spatial localization of modified sites on electrodes as well as electrodes prepared using global modification methods, such as electrochemical pretreatment. The distribution and electron-transfer activity of the attached enzyme will be mapped with fluorescence and chemiluminescence microscopy and compared to electrode activity prior to enzyme attachment. An objective is to construct redox-enzyme based sensors with improved sensitivity and time response. Ideally, this will allow the construction of microscopic arrays of active enzyme sites on a carbon-fiber substrate while leaving other sites underivatized to facilitate electron transfer reactions of redox mediators. Thus, enzyme activity can be maximized while detection of the enzyme mediator can be optimized on the unmodified carbon. The GDH- modified electrode will be used to monitor glutamate efflux following depolarization of glutamate-containing neurons of the larval fly (Musca domestica) neuromuscular junction. These axons can be stimulated independently and recording electrodes will be placed in close proximity to the neuromuscular junction, where the efflux of glutamate from adjacent nerve terminals should be observed. Therefore, this should be an ideal preparation to determine the basic characteristics of the presynaptic moduation of glutamate release without the use of vertebrate animals.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM044112-07
Application #
2459408
Study Section
Metallobiochemistry Study Section (BMT)
Project Start
1991-05-01
Project End
1999-07-31
Budget Start
1997-08-01
Budget End
1998-07-31
Support Year
7
Fiscal Year
1997
Total Cost
Indirect Cost
Name
University of California Riverside
Department
Chemistry
Type
Schools of Earth Sciences/Natur
DUNS #
City
Riverside
State
CA
Country
United States
Zip Code
92521
Rosenwald, S E; Nowall, W B; Dontha, N et al. (2000) Laser interference pattern ablation of a carbon fiber microelectrode: biosensor signal enhancement after enzyme attachment. Anal Chem 72:4914-20
Dontha, N; Nowall, W B; Kuhr, W G (1999) Development of sub-micron patterned carbon electrodes for immunoassays. J Pharm Biomed Anal 19:83-91
Hayes, M A; Kuhr, W G (1999) Preservation of NADH voltammetry for enzyme-modified electrodes based on dehydrogenase. Anal Chem 71:1720-7
Rosenwald, S E; Dontha, N; Kuhr, W G (1998) A laser ablation method for the spatial segregation of enzyme and redox sites on carbon fiber microelectrodes. Anal Chem 70:1133-40
Nowall, W B; Wipf, D O; Kuhr, W G (1998) Localized avidin/biotin derivatization of glassy carbon electrodes using SECM. Anal Chem 70:2601-6
Hayes, M A; Kristensen, E W; Kuhr, W G (1998) Background-subtraction of fast-scan cyclic staircase voltammetry at protein-modified carbon-fiber electrodes. Biosens Bioelectron 13:1297-305
Nowall, W B; Dontha, N; Kuhr, W G (1998) Electron transfer kinetics at a biotin/avidin patterned glassy carbon electrode. Biosens Bioelectron 13:1237-44
Singhal, P; Kuhr, W G (1997) Ultrasensitive voltammetric detection of underivatized oligonucleotides and DNA. Anal Chem 69:4828-32
Dontha, N; Nowall, W B; Kuhr, W G (1997) Generation of biotin/avidin/enzyme nanostructures with maskless photolithography. Anal Chem 69:2619-25
Nowall, W B; Kuhr, W G (1995) Electrocatalytic surface for the oxidation of NADH and other anionic molecules of biological significance. Anal Chem 67:3583-8

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