title: A novel electrochemical biosensor for the detection of uric acid and adenine.
abstract: A novel electrochemical biosensor for the detection of uric acid and adenine was prepared based on a gel containing multi-walled carbon nanotubes and room-temperature ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate. The electrochemistry of uric acid and adenine was studied in this gel modified electrode. There was a significant two-way electrocatalytic activity upon both oxidation and reduction of uric acid. Similar to a bare glassy carbon electrode, uric acid undergoes a 2e,2H+ oxidation in phosphate buffer in the modified electrode. A diimine, the oxidation product of uric acid, was found to be an unstable intermediate, which was converted by a follow-up hydration reaction to an imine alcohol, with the reaction rate constant of 8.5 +/- 0.3 M(-1).s(-1) according to Nicholson's theory. Under optimum conditions, linear calibration graphs were obtained over the concentration range of 1.0 x 10(-7) M approximately 1.0 x 10(-5) M (uric acid) and 1.0 x 10(-5) M approximately 6.0 x 10(-4) M (adenine). Based on the signal-to-noise ratio of 3, the detection limits of the current technique was found to be as low as 9.0 x 10(-8) M (uric acid) and 2.0 x 10(-6) M (adenine), respectively. This novel biosensor was successfully applied for the assay of uric acid in human urine. Because of its good stability and long-term durability, such a gel modified electrode can provide a simple and easy approach for sensitive detection of uric acid and adenine.
authors.affiliation: Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China.
authors.forename: Yifang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Tianle
authors.initials: T
authors.lastname: Ye
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Kou
authors.forename: Meixian
authors.initials: M
authors.lastname: Li
authors.forename: Yuanhua
authors.initials: Y
authors.lastname: Shao
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Zhu
authors.forename: Qiankun
authors.initials: Q
authors.lastname: Zhuang
mesh_terms: D000225:Adenine / Q000032:analysis*; D015374:Biosensing Techniques; D002244:Carbon / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D036103:Nanotechnology; D012680:Sensitivity and Specificity; D014527:Uric Acid / Q000032:analysis*
chemical_list: D014527:Uric Acid; D002244:Carbon; D000225:Adenine