title: Selective detection of L-glutamate using a microfluidic device integrated with an enzyme-modified pre-reactor and an electrochemical detector.
abstract: A microfluidic device integrated with a nanoliter volume enzyme pre-reactor and an enzyme-modified electrode was developed for the highly selective continuous measurement of glutamate (Glu). The device consists mainly of two glass plates. One plate incorporates an electrochemical cell that consists of working electrode (WE), reference electrode (RE) and counter electrode (CE). The WE is modified with a bilayer film of Os-polyvinylpyrridine-based mediator containing horseradish peroxidase (Os-gel-HRP). The WE was operated at -50 mV versus Ag. The other plate has a thin layer flow channel integrated with a pre-reactor. The reactor has a number of micropillars (20 microm in diameter, 20 microm high and separated from each other by a 20 microm gap) modified with ascorbate oxidase (AAOx) to eliminate L-ascorbic acid (AA). The enzymatic oxidation of AA is superior to that obtained with our previously reported pre-electrolysis type micro-reactor since electrochemically reversible transmitters such as catecholamines do not provide a cathodic current at the WE. In addition, the high operation potential of the pre-reactor causes unknown electroactive species, which also cause interference at the detection electrode. As a result, we were able to detect 1 microM Glu continuously at a low flow rate even when AA concentration was 100 microM.
authors.affiliation: NTT Microsystem Integration Laboratories, NTT Advanced Technology Corporation, 3-1, Morinosato, Wakamiya, Atsugi, Kanagawa 243-0198, Japan. kiki@aecl.ntt.co.jp
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Hayashi
authors.forename: Ryoji
authors.initials: R
authors.lastname: Kurita
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Horiuchi
authors.forename: Osamu
authors.initials: O
authors.lastname: Niwa
mesh_terms: D001205:Ascorbic Acid / Q000378:metabolism; D015374:Biosensing Techniques; D004566:Electrodes; D018698:Glutamic Acid / Q000032:analysis*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D009992:Osmium; D011145:Polyvinyls; D013997:Time Factors
chemical_list: D011145:Polyvinyls; D009992:Osmium; D018698:Glutamic Acid; D006735:Horseradish Peroxidase; D001205:Ascorbic Acid