Electrogenerated Functional Single-Walled Carbon Nanotube Composites for Biosensor Applications
Michael Holzinger
Recent approaches for the entrapment of biomolecules in single-walled carbon nanotube (SWCNT)-polymer matrices and their immobilization on nanostucured functional nanotube-polymer composites are highlighted. Stable SWCNT dispersions were obtained using an electropolymerizable surfactant. For these dispersions, commercial available SWCNTs could be used as received without any further treatment. Enzymes like glucose oxidase have been entrapped in this copolymer during electropolymerization. The resulting glucose biosensors exhibit a drastic increase of sensitivities and maximum currents compared with the same sensor setup using such electrogenerated polymer films without nanotubes.
Particular interesting results were obtained by electropolymerization of biotin- and adamantane-pyrrole derivatives onto the SWCNT sidewalls to obtain highly functional nanotube composites.
The highly porous nanotube-polypyrrole layer provided affinity interactions with β-cyclodextrin and avidin. SWCNTcoatings were thus functionalized with poly(adamantane-pyrrole) and poly(biotin-pyrrole) and applied to the anchoring of glucose oxidase (GOX), modified with β-cyclodextrin and avidin and after of biotinylated glucose oxidase, respectively. By using this affinity system adamantane-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 all these biosensors to glucose were measured by potentiostating the modified electrodes in order to oxidise the enzymatically generated hydrogen peroxide in 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 adamantane functionalized SWCNTs and GOX.
Keywords: Single-walled carbon nanotubes, electropolymerization, composites, enzymes, affinity system, biosensors, amperometry.