Nanostructured Biosensors Built by Layer-by-Layer Electrostatic Assembly of Enzyme-Coated Single-Walled Carbon Nanotubes and Redox Polymers

Abstract

In this study, we describe the construction of glucose biosensors based on an electrostatic layer-by-layer (LBL) technique. Gold electrodes were initially functionalized with negatively charged 11-mercaptoundecanoic acid followed by alternate immersion in solutions of a positively charged redox polymer, poly[(vinylpyridine)Os(bipyridyl)2Cl(2+/3+)], and a negatively charged enzyme, glucose oxidase (GOX), or a GOX solution containing single-walled carbon nanotubes (SWNTs). The LBL assembly of the multilayer films were characterized by UV-vis spectroscopy, ellipsometry, and cyclic voltammetry, while characterization of the single-walled nanotubes was performed with transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. When the GOX solution contained single-walled carbon nanotubes (GOX-SWNTs), the oxidation peak currents during cyclic voltammetry increased 1.4-4.0 times, as compared to films without SWNTs. Similarly the glucose electro-oxidation current also increased (6-17 times) when SWNTs were present. By varying the number of multilayers, the sensitivity of the sensors could be controlled.

Peroxidase Mimetic Activity at Tailored Nanocarbon Electrodes

“…1/I K = (1/nFA )(1/k 1 c*+1/k s ) [9] In these equations, c* is the bulk concentration of H 2 O 2 in solution, n is the number of electrons transferred, F is Faraday's constant (96,485 C/mol), A is the geometric area of the electrode, D is the diffusion coefficient of H 2 O 2 (1.6 x 10 -5 cm 2 /s), v is the kinematic viscosity of water (0.01 cm 2 /s), (38) is the surface coverage of the catalytic species (such as HRP or Fe), k 1 is rate of reaction between H 2 O 2 and the catalytic moiety (HRP or Fe), and k s is the turnover number of electron transfer between the catalytic moiety and the electrode.…”

Amperimetric Biosensor Based on Carbon Nanotube and Plasma Polymer

“…5. However, this suspension is less stable than that obtained by other processes using binder such as Nafion, polypyrrole, and surfactants (Hrapovic et al, 2004;Joshi et al, 2005;Wang et al, 2006;Gavalas et al, 2004;Merkoçi et al, 2005). Therefore, it is probable that the CNT layer is mechanically and electrically loose (probably slack packing).…”

Optimization of Carbon Nanotube Layer Formation on Plasma-Polymerized Thin Film for Enzyme Biosensor

“…However, this suspension is less stable than that obtained by other processes using a binder such as Nafion, polypyrrole, and surfactants. (6)(7)(8)(9)(10)14) Therefore, it is probable that the CNT layer is mechanically and electrically loose (probably due to slack packing). Combined with the subsequent plasma treatment, a high sensor response was obtained (Fig.…”

“…Recently, amperometric enzyme biosensors using CNTs have been increasingly reported. (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) The typical structure of a CNT-based amperometric biosensor is a combination of biomolecules (e.g., enzymes) and CNTs in the vicinity of an electrode. However, one requirement is that the hydrophobic surface of the CNTs must be changed to a hydrophilic surface in order to be combined with enzymes when used in the aqueous phase.…”

“…Some strategies have been reported to address this: the introduction of chemically active functional groups by the treatment of CNTs with sulfonic or nitric acid, which then enables subsequent modification. (2)(3)(4) Another strategy is the dispersion of CNTs within a matrix such as Nafion, (5,6) a redox hydrogel, (7,8) or other polymers. (9)(10)(11) However, these methods require that the enzymes and other biomolecules receive careful treatment in order to retain their tertiary structure.…”