title: Designing electrochemical interfaces with functionalized magnetic nanoparticles and wrapped carbon nanotubes as platforms for the construction of high-performance bienzyme biosensors.
abstract: The design of a novel biosensing electrode surface, combining the advantages of magnetic ferrite nanoparticles (MNPs) functionalized with glutaraldehyde (GA) and poly(diallyldimethylammonium chloride) (PDDA)-coated multiwalled carbon nanotubes (MWCNTs) as platforms for the construction of high-performance multienzyme biosensors, is reported in this work. Before the immobilization of enzymes, GA-MNP/PDDA/MWCNT composites were prepared by wrapping of carboxylated MWCNTs with positively charged PDDA and interaction with GA-functionalized MNPs. The nanoconjugates were characterized by scanning electron microscopy (SEM) and electrochemistry. The electrode platform was used to construct a bienzyme biosensor for the determination of cholesterol, which implied coimmobilization of cholesterol oxidase (ChOx) and peroxidase (HRP) and the use of hydroquinone as redox mediator. Optimization of all variables involved in the preparation and analytical performance of the bienzyme electrode was accomplished. At an applied potential of -0.05 V, a linear calibration graph for cholesterol was obtained in the 0.01-0.95 mM concentration range. The detection limit (0.85 μM), the apparent Michaelis-Menten constant (1.57 mM), the stability of the biosensor, and the calculated activation energy can be advantageously compared with the analytical characteristics of other CNT-based cholesterol biosensors reported in the literature. Analysis of human serum spiked with cholesterol at different concentration levels yielded recoveries between 100% and 103%
authors: Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, 28040 Madrid, Spain.
authors: Marcos
authors: M
authors: Eguílaz
authors: Reynaldo
authors: R
authors: Villalonga
authors: Paloma
authors: P
authors: Yáñez-Sedeño
authors: José M
authors: JM
authors: Pingarrón
mesh_terms: D015374:Biosensing Techniques; D002784:Cholesterol / Q000032:analysis / Q000097:blood; D002789:Cholesterol Oxidase / Q000737:chemistry / Q000378:metabolism*; D055664:Electrochemical Techniques; D004566:Electrodes; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry; D005976:Glutaral / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006873:Hydroquinones / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D011095:Polyethylenes / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
chemical_list: D004800:Enzymes, Immobilized; D005290:Ferric Compounds; D006873:Hydroquinones; D058185:Magnetite Nanoparticles; D037742:Nanotubes, Carbon; D011095:Polyethylenes; D000644:Quaternary Ammonium Compounds; C001215:ferrite; C041004:poly-N,N-dimethyl-N,N-diallylammonium chloride; D002784:Cholesterol; D002789:Cholesterol Oxidase; D006735:Horseradish Peroxidase; D005976:Glutaral; C031927:hydroquinone