Nanochemistry aids tissue engineering


GALVESTON, Texas, June 25 (UPI) -- Medical procedures could soon see benefits from scientists' understanding of chemical reactions among small groups of molecules or even single atoms, researchers said Tuesday at a conference.

This nanoscale chemistry could speed up blood tests for trace amounts of substances, said Leon Hirsch, a graduate student with the Department of Bioengineering at Rice University in Houston. The process, called immunoassay, is based on spheres of silicon, only a few nanometers across, coated with gold atoms, he told a session at NanoSpace 2002.


"In whole blood, we can (detect agents) on the order of minutes instead of days," Hirsch said. "We use gold because it's fairly inert and presents good biocompatibility. Furthermore, the chemistry of attaching antibodies to gold is fairly simple."

The antibodies are used to latch on to the target substance of the test, Hirsch said. If the substance is present, multiple nanospheres will clump together around it, changing the optical properties of the sample for easy detection, he explained.

Tests have shown the method can differentiate between different concentrations of a substance in as little as 10 minutes, Hirsch said. The nanosphere immunoassay has the advantage of not needing multiple incubation and rinsing steps, which prevents current technology from providing quick answers, he added.


Companies have licensed the technique to conduct research into detecting viruses and other agents, said Jennifer West, a professor of bioengineering at Rice. Similar gold-based tests have already received Food and Drug Administration approval, she said, so the nanosphere test could be fast-tracked to commercial use in a year or two.

Longer-term research is examining how doctors might use nanoscale chemistry to guide the body's mechanisms for repairing tissue. For example, nitrous oxide embedded in biocompatible polymers could improve the performance of angioplasty, a procedure for clearing blocked arteries, said Elizabeth Lipke, another researcher at Rice.

At present, angioplasty is a temporary solution to the problem -- because it expands and partly damages the arterial wall, the body's response is to refill the artery, Lipke said. Light-activated, biodegradable polymers called hydrogels can provide a mechanical barrier to tissue regrowth, but Lipke and her fellow researchers are examining ways to embed nitrous oxide in the gels.

Nitrous oxide inhibits growth of arterial muscle and helps create the cells normally lining the artery, Lipke said, resulting in a proper, longer-term arterial repair. Although the chemical can affect many systems inside the body, the hydrogel's time-released, trace amounts do not travel beyond the angioplasty site, she said.


The nitrous oxide hydrogel is another application that could see commercial use within a few years, West said.

"(This method is) moving into clinical trials this year," West told United Press International. "The base hydrogel has already been approved (by the FDA and) they're now comfortable with the idea of doing the photochemistry inside the body."

Although hydrogels and similar polymers are seeing some use as scaffolds for skin repair, researchers want to expand the technique to tissues inside the body, West said. The key to doing so lies in ensuring the scaffolds spur the growth of blood vessels as well as primary tissue, she said. Nanochemistry is expected to provide the means to this goal by embedding patterns of different cell growth factors inside the polymers.

The NanoSpace conference, sponsored by the Institute for Advanced Multidisciplinary Research, the National Aeronautics and Space Administration and several universities, was set up to help NASA and the research community work out joint goals for nanotechnology.

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