title: Carbon nanotube-chitosan system for electrochemical sensing based on dehydrogenase enzymes.
abstract: Multiwalled carbon nanotubes (CNT) were solubilized in aqueous solutions of a biopolymer chitosan (CHIT). The CHIT-induced solubilization of CNT facilitated their manipulations, including the modification of electrode surfaces for sensor and biosensor development. The colloidal solutions of CNT-CHIT were placed on the surface of glassy carbon (GC) electrodes to form robust CNT-CHIT films, which facilitated the electrooxidation of NADH. The GC/CNT-CHIT sensor for NADH required approximately 0.3 V less overpotential than the GC electrode. The susceptibility of CHIT to chemical modifications was explored in order to covalently immobilize glucose dehydrogenase (GDH) in the CNT-CHIT films using glutaric dialdehyde (GDI). The stability and sensitivity of the GC/CNT-CHIT-GDI-GDH biosensor allowed for the interference-free determination of glucose in the physiological matrix (urine). In pH 7.40 phosphate buffer solutions, linear least-squares calibration plots over the range 5-300 microM glucose (10 points) had slopes 80 mA M(-1) cm(-2) and a correlation coefficient 0.996. The detection limit was 3 microM glucose (S/N = 3). The CNT-CHIT system represents a simple and functional approach to the integration of dehydrogenases and electrodes, which can provide analytical access to a large group of enzymes for wide range of bioelectrochemical applications including biosensors and biofuel cells.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249-0698, USA.
authors.forename: Maogen
authors.initials: M
authors.lastname: Zhang
authors.forename: Audrey
authors.initials: A
authors.lastname: Smith
authors.forename: Waldemar
authors.initials: W
authors.lastname: Gorski
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D048271:Chitosan / Q000737:chemistry*; D004563:Electrochemistry; D004800:Enzymes, Immobilized / Q000737:chemistry*; D005947:Glucose / Q000032:analysis; D009243:NAD / Q000032:analysis; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D009243:NAD; D048271:Chitosan; D010088:Oxidoreductases; D005947:Glucose