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Xanthine Sensors Based on Anodic and Cathodic Detection of Enzymatically Generated Hydrogen Peroxide
Author(s) -
Rahman Md. Aminur,
Won MiSook,
Shim YoonBo
Publication year - 2007
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200603799
Subject(s) - xanthine oxidase , chemistry , xanthine , biosensor , hydrogen peroxide , quartz crystal microbalance , cyclic voltammetry , detection limit , inorganic chemistry , x ray photoelectron spectroscopy , nuclear chemistry , electrochemistry , organic chemistry , electrode , chromatography , enzyme , chemical engineering , biochemistry , adsorption , engineering
A xanthine biosensor was fabricated by the covalent immobilization of xanthine oxidase (XO) onto a functionalized conducting polymer (Poly‐5, 2′: 5′, 2″‐terthiophine‐3‐carboxylic acid), poly‐TTCA through the formation of amide bond between carboxylic acid groups of poly‐TTCA and amine groups of enzyme. The immobilization of XO onto the conducting polymer (XO/poly‐TTCA) was characterized using cyclic voltammetry, quartz crystal microbalance (QCM), and X‐ray photoelectron spectroscopy (XPS) techniques. The direct electron transfer of the immobilized XO at poly‐TTCA was found to be quasireversible and the electron transfer rate constant was determined to be 0.73 s −1 . The biosensor efficiently detected xanthine through oxidation at +0.35 V and reduction at −0.25 V (versus Ag/AgCl) of enzymatically generated hydrogen peroxide. Various experimental parameters, such as pH, temperature, and applied potential were optimized. The linear dynamic ranges of anodic and cathodic detections of xanthine were between 5.0×10 −6 −1.0×10 −4 M and 5.0×10 −7 to 1.0×10 −4 M, respectively. The detection limits were determined to be of 1.0×10 −6 M and 9.0×10 −8 M with anodic and cathodic processes, respectively. The applicability of the biosensor was tested by detecting xanthine in blood serum and urine real samples.