Biosensors Based on Carbon Nanotubes
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Carbon nanotube (CNT) is an attractive material for the development of biosensors because of its capability to provide strong electrocatalytic activity and minimize surface fouling of the sensors. This article reviews the recent successful development of biosensors based on CNT materials. Specifically, biosensors from two fabrication regimes have been investigated: 1) the coimmobilization of CNTs and enzymes on electrode surfaces and 2) the growth of controlled-density aligned CNTs for the fabrication of nanoelectrode arrays. In the first regime, the CNTs are either dispersed in solvents [e.g., sulfuric acid, dimethylformamide (DMF)], dissolved in Nafion solution for electrode coating, or mixed with Teflon as an electrode material for reagentless biosensors. In the second regime, the nanoelectrode arrays consisting of millions of vertically aligned CNTs, each acting as an individual electrode, have been fabricated through a nonlithographic method. We also demonstrate the capability of CNTs to promote the oxidation/reduction (redox) reactions of hydrogen peroxide and nicotinamide adenine dinucleotide (NADH), which are involved in a wide range of amperometric biosensors associated with oxidase and dehydrogenase enzymes, respectively. With these electrocatalytic properties of CNTs, the applications of CNT-based biosensors examined in our laboratories include the low-potential detections of glucoses, organophosphorous compounds, and alcohol.