title: Direct electrochemistry of cholesterol oxidase immobilized on gold nanoparticles-decorated multiwalled carbon nanotubes and cholesterol sensing.
abstract: An electrochemical cholesterol biosensor based on the direct electron transfer of cholesterol oxidase (ChOx) immobilized on gold nanoparticles-decorated multiwalled carbon nanotubes (GNPs-MWCNTs) was fabricated. GNPs-MWCNTs were prepared based on the reduction of HAuCl4 in the presence of carboxyl group functionalized MWCNTs. Transmission electron microscopy image shows that rounded gold nanoparticles with diameters of 6-10nm were decorated on carbon nanotube surfaces. ChOx was directly adsorbed on the nanocomposite modified glassy carbon electrode and protected by a Nafion film. Direct electrochemistry of ChOx on the electrode surface was obtained, proved by one pair of well-defined, quasi-reversible redox peaks in phosphate buffered saline. Under optimized conditions, the fabricated electrode displayed a linear response in the cholesterol concentration range from 0.0100 to 5.00 mmol L(-1) with a detection limit of 4.3 μmol L(-1) estimated at a signal-to-noise ratio of 3. The apparent Michaelis-Menten constant was measured to be 0.29 mmol L(-1), indicating that the immobilized ChOx on GNPs-MWCNTs matrix retained its native activity. The developed biosensor presented good selectivity, repeatability, reproducibility and stability. The concentration of free cholesterol in a human serum sample, detected by using the developed biosensor, is in good agreement with that determined by the well-established spectrophotometric method.
authors.affiliation: Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research (Ministry of Education of China), College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, China.
authors.forename: Lian
authors.initials: L
authors.lastname: Zhu
authors.forename: Lili
authors.initials: L
authors.lastname: Xu
authors.forename: Liang
authors.initials: L
authors.lastname: Tan
authors.forename: Hao
authors.initials: H
authors.lastname: Tan
authors.forename: Sufang
authors.initials: S
authors.lastname: Yang
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D002784:Cholesterol / Q000097:blood*; D002789:Cholesterol Oxidase / Q000737:chemistry*; D055664:Electrochemical Techniques; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D057230:Limit of Detection; D037742:Nanotubes, Carbon / Q000737:chemistry*; D015203:Reproducibility of Results; D059629:Signal-To-Noise Ratio
chemical_list: D004800:Enzymes, Immobilized; D037742:Nanotubes, Carbon; D006046:Gold; D002784:Cholesterol; D002789:Cholesterol Oxidase