title: Nano-molar level hydrogen peroxide detection by horseradish peroxidase adsorbed cup-stacked carbon nanotube electrodes and applications to L-glutamate detection.
abstract: We have developed a simple fabrication method of a highly sensitive direct electron transfer-type electrochemical biosensor for hydrogen peroxide by use of cup-stacked carbon nanotubes (CSCNTs). The CSCNTs, formed by stacking of cup-shaped carbon units, has larger internal space and more hydrophilic edges, thanks to the presence of functional groups containing oxygen (e.g., -COOH, -OH), than multi-walled carbon nanotubes (MWCNTs). When the CSCNTs suspension was cast, the CSCNTs were dispersed homogeneously onto a glassy carbon (GC) electrode, and horseradish peroxidase (HRP) was immobilized firmly by physical adsorption without any chemical reactions. The flow injection analysis (FIA) system with the HRP/CSCNTs/GC electrode has superior sensitivity and stability to the HRP/MWCNTs/GC electrode. The detection limit was 0.75 nM (S/N = 3) and the activity was maintained over 85% for 21 days. Further, when the glutamate oxidase (GlOD)-immobilized reactor was set into the proposed FIA system, L-glutamate could be detected repeatedly with a detection limit of 1.2 nM (S/N = 3).
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo, Kyoto 606-8502, Japan. nodat@kais.kyoto-u.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Noda
authors.forename: Tadao
authors.initials: T
authors.lastname: Ukai
authors.forename: Toshio
authors.initials: T
authors.lastname: Yao
mesh_terms: D000327:Adsorption; D015374:Biosensing Techniques / Q000379:methods*; D004563:Electrochemistry; D004566:Electrodes; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D017022:Flow Injection Analysis; D005898:Glass / Q000737:chemistry; D018698:Glutamic Acid / Q000032:analysis* / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000032:analysis* / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D006735:Horseradish Peroxidase