20 janvier, 2006 02:22

Old medical cure, silver, is new tool to fight infection

The New York Times

Silver, one of humankind's first weapons against bacteria, is receiving new respect for its antiseptic powers, thanks to the growing ability of researchers to tinker with its molecular structure.

Doctors used silver to fight infections at least as far back as the days of ancient Greece and Egypt. Their knowledge was absorbed by Rome, where historians such as Pliny the Elder reported that silver plasters caused wounds to close rapidly.

In 1884, a German doctor named C.S.F. Crede demonstrated that a few drops of silver nitrate into the eyes of babies born to women with venereal disease virtually eliminated the risk of blindness among such infants.

But silver's time-tested if poorly understood versatility as a disinfectant was overshadowed in the latter half of the 20th century by the rise of antibiotics.

Now, with more and more bacteria developing resistance to antibiotic drugs, some researchers and health-care entrepreneurs have returned to silver for another look. This time around, they are armed with nanotechnology, a fast-developing collection of products and skills that help researchers deploy silver compounds in ways that maximize the availability of silver ions -- the element's most potent form. Scientists also now have a better understanding of the weaknesses of their microbial adversaries.

One of the urgent goals is to prevent bacterial infections that each year strike 2 million hospital patients and kill 90,000, according to the Centers for Disease Control and Prevention. Such infections usually are treated with large doses of antibiotics and sometimes with repeat surgeries. They cost the health-care system roughly $4.5 billion annually, and the challenge is growing with the spread of drug-resistant microbes.

The latest advance for silver therapy comes from AcryMed, a company in Portland, Ore., that has invented a process to deposit silver particles averaging about 10 nanometers -- less than a thousandth the diameter of a human hair -- on medical devices. AcryMed's first customer, I-Flow, makes a silver-coated catheter that pumps painkillers into wounds from surgery.

I-Flow got federal regulatory clearance on Dec. 2 to sell the devices and has begun shipping them to customers. The nanoscale particles have so much surface area to react with the microbes, in relation to their volume, that small concentrations are effective antiseptics.

"The equivalent of a teaspoon of silver in a seven-lane Olympic-size swimming pool is enough to do the job," said Bruce Gibbons, the microbiologist who is AcryMed's founder and chief executive.

AcryMed hopes to reach agreements with catheter companies larger than I-Flow, including the makers of urinary catheters, the most common breeding ground for hospital infections. Eventually, nanoscale silver also could make its way onto permanently implanted devices such as silicone breast implants, artificial hips and knees, and pacemakers.