title: Ion channel sensors for glutamic acid.
abstract: Coulometric biosensors using glutamate receptor (GluR) ion channel protein as a signal-amplifying sensory element that exploit the glutamate-triggered Na+ ion current through bilayer lipid membranes have been fabricated. The formation of stable planar bilayer lipid membranes was achieved by applying the folding method across a small circular aperture bored through a thin polyimide film. The multichannel type sensing membranes, formed across an aperture of ca. 120 microns diameter, contained more than 10 GluR proteins and showed L-glutamate-triggered response as a composite of individual single-channel currents. The single-channel type sensing membranes, formed across an aperture of ca. 20 microns diameter, contained a sufficiently small number of GluR proteins so that the response was observed as a series of single-channel pulse currents. Dependence of the integrated channel current on the glutamate concentration was examined. A sharp concentration dependence of up to ca. 1.5 x 10(-7) M and 3 x 10(-6) M for the multichannel and single-channel type sensors, respectively, was observed. A high selectivity for L-glutamate compared with D-glutamate for inducing the channel current was observed. A detection limit as low as ca. 3 x 10(-8) M was attained for the multichannel type sensor. This remarkable sensitivity is discussed in terms of the potential use of GluR ion channel protein for a new type of sensing system.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Minami
authors.forename: M
authors.initials: M
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Odashima
authors.forename: Y
authors.initials: Y
authors.lastname: Umezawa
authors.forename: M
authors.initials: M
authors.lastname: Uto
authors.forename: E K
authors.initials: EK
authors.lastname: Michaelis
authors.forename: T
authors.initials: T
authors.lastname: Kuwana
mesh_terms: D015374:Biosensing Techniques; D005971:Glutamates / Q000032:analysis*; D018698:Glutamic Acid; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000502:physiology
chemical_list: D005971:Glutamates; D007473:Ion Channels; D008051:Lipid Bilayers; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D018698:Glutamic Acid