Wiring enzymes to sense biochemicals.

Wiring enzymes to sense biochemicals

Devices that quickly measure a target compound in a solution teeming with thousands of different chemicals entice scientists and businesspeople alike. Enzymes -- nature's own chemical manipulators -- offer one strategy for making such picky sensors. Scientists have long sought to emulate enzymes' ability to bind and rearrange specific molecules. Now, Adam Heller of the University of Texas in Austin and his colleagues have begun tailoring a new class of biosensors by attaching certain electron-juggling enzymes to hair-thin carbon electrodes, using polymers as connecting "wires." One of their more promising experimental models apparently measures blood glucose levels more rapidly and precisely than existing diagnostic tests.

Making a glucose sensor, they find, can be as simple as immersing a carbon fiber into two solutions: first into a polymer solution of polyvinylpyridine molecules studded with osmium-containing groups, and then into a bath of glucose oxidase, a commercially available enzyme. "Two dips produces a useful electrode," Heller reports.

Molecules of the stringly polymer squiggle into crevices of the overlying enzyme molecules. When the resulting biosensor contacts a sample, such as a drop of blood, glucose molecules oxidize by giving up an electron. The osmium-centered relay stations hurriedly pass the electrons, like hot potatoes, to the carbon surface. The electrical signal reaching the carbon electrode is proportional to glucose levels in the sample.

This diagnostic system, already under evaluation in a French hospital and German medical school, could mean big business since millions of diabetics monitor their blood glucose levels every day.