Worth more than its weight in silver for burns

New medical dressings are reinforcing the lesson that, for burn patients, silver is worth more in a bandage than in bullion.

Silver's antibiotic properties have made the precious metal a popular treatment for wounds and burns. It helps skin to heal by staving off infections. In recent years several companies, including Nucryst Pharmaceuticals Corp. of Wakefield, have revolutionized wound care with silver-impregnated dressings that require fewer painful changings than previous silver treatments.

Now Nucryst says it is poised for a round of growth. At the end of April federal regulators told the company and its marketing partner, Smith & Nephew PLC, that in addition to selling sheets of the dressing, which the two firms introduced in 1998, they could offer a foam version. Both products are called Acticoat.

Doctors hope the foam will let them treat deeper injuries that sheets can't reach, such as bedsores. ''There's a versatility to this product," said Robert H. Demling, a director of Brigham and Women's Hospital Burn Center in Boston, and a scientific adviser to Nucryst.

Other companies recently have brought silver-based treatments to market, including Johnson & Johnson's Ethicon wound-care division, Bristol-Myers Squibb Co. -- whose gel ''Aquacel Ag" is named after the symbol for silver on the Periodic Table -- and Medline Industries Inc. of Illinois.

Jonathan Primer, president of Medline's advanced wound and skincare division, said the demand for silver-based dressings is growing in response to concerns that some bacteria are becoming resistant to antibiotic drugs. ''To be able to add an antimicrobial element, in an environment where there are all sorts of well-known resistances, that really is revolutionary," he said.

Head-to-head clinical trials of the various products against each other are scarce, and doctors say each has advantages for certain types of wounds. For instance, Nucryst's new foam can be applied to wet wounds to absorb excess fluids, or moistened to deliver water to a dry wound.

Also, many of the products are used in conjunction with other technologies like skin substitutes, skin taken from unburned body parts, and biomaterials that foster cell growth.

Primer estimates the total market for silver dressings at about $40 million annually. Smith & Nephew puts it at $50 million, up 82 percent from 2003. Market-research firm Frost & Sullivan estimates US sales last year at $75 million.

While $75 million is not a startling figure in the field of medical devices -- where hit products like cardiac stents or defibrillators can generate annual sales of $1 billion or more -- the attention silver dressing are receiving from some of the largest device companies demonstrates their interest in driving innovations even in niche markets.

The cleansing power of silver was known in the days of the Roman Empire, when silver coins were placed in jugs of water to help keep them pure. The metal seems to disable an enzyme that many types of bacteria use to generate energy. Also, silver isn't toxic to human tissue, unlike heavy metals such as cadmium.

Doctors began using silver solutions for wound care in the 1930s. That gave way to drugs like silver sulfadiazine, which is made up of silver particles in a cream applied directly to the wound. But the silver particles were released quickly so the cream had to be changed twice a day, which could involve painful dressing changes.

Nucryst, owned by Westaim Corp. of Calgary, Alberta, uses a nanotechnology process that allows it to impregnate its dressings with smaller silver crystals. The process was invented by a Canadian scientist whose work the company continues at its lab near Edmonton, Alberta. Nucryst also has 30 employees in Wakefield.

Scott Gillis, Nucryst president, said its work in nanotechnology has drawn more attention to the company in recent years. Nanotechnology involves the rearrangement of atoms and molecules.

''We always viewed ourselves as a healthcare company first, that happened to be using nanotechnology," Gillis said. ''Now that nanotechnology is hot, I've been invited to speak at a number of events."

To create Acticoat, Nucryst technicians barrage sheets of polyethylene mesh with charged silver particles. The resulting crystals are 10 nanometers wide, compared with 250 nanometers for normal silver crystals. A nanometer is one-billionth of a meter. The smaller crystals allow a large amount of silver to interact with and pass into human tissue. That means the Acticoat can last for up to a week without being changed. Its durability helps doctors keep patients more stable and to minimize their pain.

Jim Lodigiani, president of Smith & Nephew's US wound management division, said the product is one of several designed for hospitals and acute-care facilities, rather than its traditional nursing home market.

Dr. Bohdan Pomahac, of Brigham and Women's Hospital in Boston, said Acticoat is the treatment most often used for third-degree burn victims. Pomahac said the main drawback of the sheets is that it is difficult to keep them in contact with some irregular or hard-to-reach wounds. He hasn't tried the foam version, but hopes it will be easier to apply. ''Something like a gel or a foam would solve that [application] problem; it would follow the contours of the surface," Pomahac said.

Ross Kerber can be reached at kerber@globe.com.