Adamantane/beta-cyclodextrin affinity biosensors based on single-walled carbon nanotubes

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 0.95V in acetonitrile, the resulting polypyrrole film provided affinity interactions with beta-cyclodextrin. SWCNT coatings were thus functionalized with poly(adamantane-pyrrole) and applied to the anchoring of glucose oxidase (COX), modified with beta-cyclodextrin. By using this affinity system adamantine-cyclodextrin, beta-cyclodextrin-modified gold nanoparticles were attached onto the functionalized SWCNT deposit as intermediate layer. This allows the immobilization of adamantane-tagged COX. The responses of these biosensors to glucose were measured by potentiostating the modified electrodes at 0.7V 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 beta-cyclodextrin-modified gold particles as intermediate layer between adamantine-functionalized SWCNTs and COX (31.02 mA M(-1)cm(-1) and 350 mu Acm(-2), respectively). The similar configuration without SWCNTs exhibits a sensitivity and J(max) of 0.98 mA M(-1)cm(-2) and 75 mu Acm(-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. (c) 2008 Elsevier B.V. All rights reserved.