A two-dimensional imaging biosensor to monitor enhanced brain glutamate release stimulated by nicotine

In this study, we have imaged and monitored real-time release of neurotransmitter glutamate from mouse brain slices stimulated by nicotine and physiological salts using a newly developed two-dimensional (2D) imaging biosensor. Nicotine, the addictive substance contained in cigarettes and other tobacco baring products, affects human body through interactions with both central and peripheral nervous system receptors and exists in various concentrations in body organs including the brain. The 2D imaging biosensor, designed for sensitive glutamate monitoring, is prepared through the use of a flat silica plate that is covalently attached with an enzyme, glutamate dehydrogenase (GDH). The 2D imaging biosensor can spatially resolve glutamate release and has a detection limit of 40 nM in detecting glutamate release from glutaminergic neurons in the brain slices. Using this biosensor, we have shown that the administration of nicotine (50 nM) on the brain slice stimulates repetitive glutamate release. To the best of our knowledge, this is the first time that a biosensor was used to define the vital role of nicotine in glutamate release. Physiological salts such as KCl and CaCl(2) have also been used to characterize the biosensor in measuring glutamate release. It is found in this study that nicotine stimulation is much more potent than physiological salts. The real-time detection of newly released glutamate from mouse brain slices clearly demonstrates the feasibility of the two-dimensional glutamate biosensor for real-time monitoring of dynamic glutamate release from living specimen.