doi:10.1016/j.bios.2008.06.029
Copyright © 2008 Elsevier B.V. All rights reserved.
Adamantane/β-cyclodextrin affinity biosensors based on single-walled carbon nanotubes
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Michael Holzingera, 
, 
, Laurent Bouffiera, Reynaldo Villalongab and Serge Cosniera
aDépartement de Chimie Moléculaire, UMR-5250, ICMG FR-2607, CNRS, Université Joseph Fourier, Grenoble, France
bCenter for Enzyme Technology, University of Matanzas, Cuba
Received 13 April 2008;
revised 9 June 2008;
accepted 16 June 2008.
Available online 28 June 2008.
Abstract
One challenging goal for the development of biosensors is the conception of three-dimensional biostructures on electrode surfaces. With the aim to develop 3D architectures based on single-walled carbon nanotubes (SWCNTs) frameworks a novel adamantane-pyrrole monomer was synthesized. After electrochemical polymerization at 0.95 V in acetonitrile, the resulting polypyrrole film provided affinity interactions with β-cyclodextrin. SWCNT coatings were thus functionalized with poly(adamantane-pyrrole) and applied to the anchoring of glucose oxidase (GOX), modified with β-cyclodextrin. By using this affinity system adamantine–cyclodextrin, β-cyclodextrin-modified gold nanoparticles were attached onto the functionalized SWCNT deposit as intermediate layer. This allows the immobilization of adamantane-tagged GOX. The responses of these biosensors to glucose were measured by potentiostating the modified electrodes at 0.7 V versus saturated calomel electrode (SCE) in order to oxidize the enzymatically generated hydrogen peroxide in the presence of glucose and oxygen. The highest sensitivity and maximum current density were recorded for the configuration based on β-cyclodextrin-modified gold particles as intermediate layer between adamantine-functionalized SWCNTs and GOX (31.02 mA M−1cm−2 and 350 μA cm−2, respectively). The similar configuration without SWCNTs exhibits a sensitivity and Jmax of 0.98 mA M−1cm−2 and 75 μA cm−2, respectively. The resulting supramolecular assemblies were characterized by scanning electron microscopy (SEM). Advantages and disadvantages of the different preparation methods and the performance of each affinity sensor setup are discussed in detail.
Keywords: Single-walled carbon nanotubes; Functionalization; Electropolymerization; 3D affinity biosensors
Fig. 1. (A) Schematic presentation of mono-6-deoxy-6-amino-β-cyclodextrin (β-CD); (B) reaction scheme of the electrogeneration of a thin layer of poly(adamantane-pyrrole) on the electrode surface and (C) schematic presentation of the polymerized adamantane/β-cyclodextrin complex. The principle of the supramolecular assembly is sketched with β-CD-tagged GOX and adamantine-modified electrodes.
Fig. 2. (A) Cyclic voltammogram of the adamantane-pyrrole monomer (2.7 mM) recorded at a Pt-disk electrode in CH3CN + 0.1 M TBAP; (B) oxidative polymerization of the pyrrole derivative by repeated potential scanning between −0.2 and 0.8 V and (C) characterization of the adamantane-polypyrrole film after transfer in CH3CN + 0.1 M TBAP free of monomer. Potentials measured versus the 10 mM Ag+/Ag in CH3CN reference electrode; scan rate 100 mV s−1.
Fig. 3. Schematic presentations and SEM images of the electropolymerized poly(adamantane-pyrrole) film (A) before and (B) after incubation in β-CD-modified gold nanoparticles.
Fig. 4. Schematic presentations and SEM images of the poly(adamantane-pyrrole) film electrogenerated on a SWCNT deposit (A) before and (B) after incubation in β-CD-modified gold nanoparticles.
Fig. 5. Sketch of the enzyme electrode configurations with (c and d) and without (a and b) an additional intermediate layer of β-CD gold nanoparticles. Calibration curves for glucose obtained at β-cyclodextrin-tagged GOX–poly(adamantane-pyrrole) electrodes (a) regular film, (b) over-oxidized film. Calibration curves for glucose obtained at adamantane-tagged GOX–β-CD-modified gold nanoparticles–poly(adamantane-pyrrole) electrodes, (c) regular film and (d) over-oxidized film. Applied potential 0.7 V versus SCE; 0.1 M phosphate buffer (pH 7).
Fig. 6. Sketch of SWCNT electrodes and related calibration curves for glucose. (a) pure SWCNT coating, (b) SWCNTs covered by a poly(adamantane-pyrrole) film, post-functionalized by β-cyclodextrin-tagged GOX and (c) SWCNTs covered by a poly(adamantane-pyrrole) film, post-functionalized by adamantane-tagged GOX with β-CD gold nanoparticles as intermediate layer. Experimental conditions as in Fig. 5.
Corresponding author. Tel.: +33 4 76 51 41 38; fax: +33 4 76 51 42 67.
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