Nanostructured Biosensors Built by Layer-by-Layer Electrostatic\nAssembly of Enzyme-Coated Single-Walled Carbon Nanotubes and\nRedox Polymers

Abstract

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