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Posted: Jul 03, 2006
A zinc oxide nanocomb biosensor for glucose detection
(Nanowerk Spotlight) New research shows that ZnO nanostructures are suitable for electrochemical biosensors. The enzyme used for glucose detection, glucose oxidase, was attached to ZnO nanocombs which resulted in a biosensor that exhibits a high affinity, high sensitivity, and fast response for glucose detection. This simple method of fabricating a ZnO based biosensor can be extended to immobilize other enzymes and other bioactive molecules on various 1D metal oxide nanostructures, and form versatile electrodes for biosensor studies.
Professor Xiaowei Sun from the School of Electrical and Electronic Engineering at Nanyang Technological University in Singapore, one of the report's authors, explains to Nanowerk: "We found that ZnO nanostructures, nanocombs in our case, can effectively modify the gold electrodes in the application of electrochemical biosensing." Sun explains several unique aspects of ZnO:
(1) A large isoelectric point (IEP) of 9.5, which allows it to attract low IEP proteins in a neutral solution by electrostatic attraction. This is a strong force that makes ZnO a better material to immobilize proteins (in our case, glucose oxidase);
(2) ZnO is a transparent conductor traditionally used as transparent electrodes for flat panel displays and solar cells, meaning it is a good electron communicator which can collect electrons generated in oxidizing glucose very efficiently and send them to the gold electrodes;
(3) ZnO nanostructures have large surface areas, indicating the device is sensitive and has fast response; in particular our nanocomb forms a dense network for large loading of enzyme and charge transferring channels;
(4) Other advantages include nontoxicity, chemical stability, and preserving the activity of the enzyme loaded.
SEM image of a ZnO nanocomb (Reprinted with permission from the American Institute of Physics)
"Typical electrochemical glucose biosensors using gold electrodes have low sensitivity" explains Sun. "Using our ZnO nanocomb electrodes, high loading of enzyme can be realized to enable a high sensitivity biosensor. Moreover, our ZnO nano electrodes can be used for other biosensors by changing the enzyme."
"Historically, we have been working on ZnO and its nanostructures, and we are constantly looking for new applications of these nanostructures" says Sun. "Looking ahead, we can expect a cheap and high sensitivity biosensor as a result of our work. Of course, we need to do more experiments to test out the durability and some manufacturing issues."