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Enzyme activity at the flick of a switch
14 August 2007
Joseph Wang at Arizona State University, Tempe, US, and co-workers have used a combination of nanowires and nanotubes to create a switchable bioelectronic device for the on-demand transformation of alcohols to aldehydes.
Wang's system uses nickel-gold nanowires, which have an enzyme trapped halfway along them, in combination with an electrode coated with carbon nanotubes. The orientation of the nanowires in the device can be switched from vertical to horizontal by a magnetic field.
A magnetic field is used to make the enzyme-modified nanotubes change position.
In the horizontal position, contact between the enzyme and the electrode allows the enzyme - in this case alcohol dehydrogenase (ADH) - to catalyse the transformation of ethanol to acetaldehyde. Regeneration of the enzyme's cofactor (NAD+) by the nanotube surface maintains the catalytic activity, and allows analysis by electrochemical methods. This means the device could be used as an alcohol sensor.
When the nanowires are switched to the vertical position, the reaction is inhibited because the enzyme has no contact with the electrode. Wang says this switchability could hold great promise for regulating the operation of biofuel cells or bioreactors.
Frederic Barriere, an expert in bioelectrochemistry at the University of Rennes, France, sees of the advantages of Wang's system over established methods. 'The oxidation of NADH on traditional electrodes quickly fails because of adsorption and surface fouling. The use of electrodes coated with acid-purified carbon nanotubes avoids this problem,' said Barriere.
Link to journal article
Adaptive nanowire–nanotube bioelectronic system for on-demand bioelectrocatalytic transformations
Rawiwan Laocharoensuk, Andrea Bulbarello, Saverio Mannino and Joseph Wang, Chem. Commun., 2007, 3362