Scientists resurrecting use of silver as antiseptic

NY Times
Dec. 22, 2005

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 prescribed 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 like Pliny the Elder reported that silver plasters caused wounds to close rapidly. More recently, in 1884, a German doctor named C.S.F. Crede demonstrated that putting a few drops of silver nitrate into the eyes of babies born to women with venereal disease virtually eliminated the high rates 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 helps 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 in the United States and kill 90,000, according to the Centers for Disease Control and Prevention. Such infections are usually treated with large doses of antibiotics and sometimes with repeat surgeries. They cost the U.S. 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 small company in Portland, Oregon, 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 the wounds created by surgery.

I-Flow got regulatory clearance in the United States on Dec. 2 to sell the device and has already begun device and has already 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. Nano-scale silver could also eventually make its way onto permanently implanted devices like silicone breasts, artificial hips and knees and pacemakers.

The term nanotechnology is derived from the nanometer, one-billionth of a meter. Nanoscale materials often exhibit unusual structures and behaviors compared with bulkier quantities of the same material.