Enzyme-Coated Gold Nanoparticles Detect Biologic Molecules

By attaching the enzyme glucose oxidase to microscopic gold crystals, researchers have fashioned a sensitive, inexpensive, and noninvasive electrode detector for glucose in the blood. Their work was reported in the March 21, 2003, issue of Science.

Gold crystals or nanoparticles only 1.4 nm in diameter are the matrix for the detection system. The gold particles specifically orient the binding of glucose oxidase to the electrode in a very ordered attachment. Since gold is an excellent conductor of electricity, it provides a path for the flow of electrons.

As the enzyme oxidizes glucose, electrons flow through the gold nanoparticle into the electrode. The more glucose present in the sample, the higher the current. The electron transfer turnover rate of the gold-glucose oxidase electrode is about 5,000 per second, compared with the rate at which molecular oxygen, the natural co-substrate of the enzyme, accepts electrons (about 700 per second). Measurement of glucose using this system is not affected by the levels of other substances that can interfere with accurate glucose readings, such as oxygen and ascorbic acid.

According to the developers of the method, from Brookhaven National Laboratory (Upton, NY, USA) and the Hebrew University of Jerusalem (Israel), "Many other substances could be attached to electrodes in this way and used to sensitively and easily detect other biological molecules, such as bioterrorism agents or other disease markers.”



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Brookhaven National Laboratory Brookhaven National Laboratory
Hebrew University of Jerusalem