title: Amperometric detection of L-lactate using nitrogen-doped carbon nanotubes modified with lactate oxidase.
abstract: Nitrogen-doped carbon nanotubes (N-CNTs) provide a simple, robust, and unique platform for biosensing. Their catalytic activity toward the oxygen reduction reaction (ORR) and subsequent hydrogen peroxide (H(2)O(2)) disproportionation creates a sensitive electrochemical response to enzymatically generated H(2)O(2) on the N-CNT surface, eliminating the need for additional peroxidases or electron-transfer mediators. Glassy carbon electrodes were modified with 7.4 atom % N-CNTs, lactate oxidase (LOx), and a tetrabutylammonium bromide (TBABr)-modified Nafion binder. The resulting amperometric l-lactate biosensors displayed a sensitivity of 0.040 ± 0.002 A M(-1) cm(-2), a low operating potential of -0.23 V (vs Hg/Hg(2)SO(4)), a repeatability of 1.6% relative standard deviation (RSD) for 200 μM samples of lactate, a fabrication reproducibility of 5.0% (RSD), a limit of detection of 4.1 ± 1.6 μM, and a linear range of 14-325 μM. Additionally, over a 90 day period, the repeatability for 200 μM samples of lactate remained below 3.4% (RSD). Direct electron transfer was observed between the LOx redox-active center and the N-CNTs with the electroactive surface coverage determined to be 0.27 nmol cm(-2).
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Goran
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Lyon
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Stevenson
mesh_terms: D015374:Biosensing Techniques; D002384:Catalysis; D004563:Electrochemistry; D004566:Electrodes; D006861:Hydrogen Peroxide / Q000737:chemistry; D019344:Lactic Acid / Q000737:chemistry; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism; D037742:Nanotubes, Carbon; D009584:Nitrogen / Q000737:chemistry*; D010084:Oxidation-Reduction; D010376:Pediococcus / Q000201:enzymology
chemical_list: D037742:Nanotubes, Carbon; D019344:Lactic Acid; D006861:Hydrogen Peroxide; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase; D009584:Nitrogen