McLamore ES, Mohanty S, Shi J, Claussen J, Jedlicka SS, Rickus JL, Porterfield DM. A self-referencing glutamate biosensor for measuring real time neuronal glutamate flux.
J Neurosci Methods 2010;
189:14-22. [PMID:
20298719 DOI:
10.1016/j.jneumeth.2010.03.001]
[Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 01/14/2010] [Accepted: 03/02/2010] [Indexed: 01/21/2023]
Abstract
Quantification of neurotransmitter transport dynamics is hindered by a lack of sufficient tools to directly monitor bioactive flux under physiological conditions. Traditional techniques for studying neurotransmitter release/uptake require inferences from non-selective electrical recordings, are invasive/destructive, and/or suffer from poor temporal resolution. Recent advances in electrochemical biosensors have enhanced in vitro and in vivo detection of neurotransmitter concentration under physiological/pathophysiological conditions. The use of enzymatic biosensors with performance enhancing materials (e.g., carbon nanotubes) has been a major focus for many of these advances. However, these techniques are not used as mainstream neuroscience research tools, due to relatively low sensitivity, excessive drift/noise, low signal-to-noise ratio, and inability to quantify rapid neurochemical kinetics during synaptic transmission. A sensing technique known as self-referencing overcomes many of these problems, and allows non-invasive quantification of biophysical transport. This work presents a self-referencing CNT modified glutamate oxidase biosensor for monitoring glutamate flux near neural/neuronal cells. Concentration of basal glutamate was similar to other in vivo and in vitro measurements. The biosensor was used in self-referencing (oscillating) mode to measure net glutamate flux near neural cells during electrical stimulation. Prior to stimulation, the average influx was 33.9+/-6.4 fmol cm(-2)s(-1)). Glutamate efflux took place immediately following stimulation, and was always followed by uptake in the 50-150 fmol cm(-2)s(-1) range. Uptake was inhibited using threo-beta-benzyloxyaspartate, and average surface flux in replicate cells (1.1+/-7.4 fmol cm(-2)s(-1)) was significantly lower than uninhibited cells. The technique is extremely valuable for studying neuropathological conditions related to neurotransmission under dynamic physiological conditions.
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