An expert debunks common myths and considers future possibilities for the use oftopical nanosilver in wound healing.
Silver has been used for centuries in many facets of life ranging from food storage to wound care, according to Adam Friedman, M.D., F.A.A.D. But silver has become more mainstream in the early 1900s and especially after the 1920s when the U.S. Food and Drug Administration approved it as a treatment.
Despite its longevity, the use of silver continues to remain a hot topic to this day, says Dr. Friedman, associate professor of dermatology, residency program director and director of translational research in the department of dermatology at The George Washington University School of Medicine & Health Sciences.
Some of that conversational staying power could have to do with the level of misunderstanding surrounding the topic.
MRSA infected surgical site left to heal by secondary intention treated with nanocrystalline silver dressing (Acticoat). One week after dressing application (changed every other day), re-epithelialization is visualized along the periphery of the ulcer and healthy granulation tissue is appreciated in the wound bed.According to Dr. Friedman, silver isn’t used as readily as it could be largely due to a number of common misperceptions;1 the first of which is that silver dressings don’t improve healing rates. Systematic reviews and meta-analyses have confirmed the positive effects of silver when dressings are used appropriately.
Another common myth is that silver dressings cause systemic toxic effects such as argyria, a condition that can turn the skin a blueish hue. Silver dressings, he explains, are unlikely to cause true argyria because only low levels of silver are used.
The idea that silver dressings delay healing and make bacteria resistant to antibiotics is another misperception.
Terminology can also contribute to the confusion since some physicians use colloidal silver and silver sulfadiazine almost interchangeably. “They are absolutely not the same,” Dr. Friedman says. “I think it is important to delineate between those very different wound medicines, as there is a growing body of evidence demonstrating that silver sulfadiazine can actually delay wound healing.”
Next: Why nano? And What's next?
Silver is most effective when there is a heavy bacterial contamination or infection. Silver is really meant for the early stages, he explains. Once you’re past that initial inflammatory stage of wound healing, typically when infection would set in, the impact of silver on wound healing is not as strong.
Scanning electron microscopy of silver nanoparticles. Scale bar 200 nm“It’s really in the initial phases that silver would be used to kill any possible invader that can slow things down,” he says. The purpose is twofold. It clears the path for wound healing to commence and progress, but it can also be a very potent antimicrobial agent. “The exciting element and interest in silver is that it physically destroys the pathogen.”
The real evolution of colloidal silver in wound care has been using nanosilver, Dr. Friedman points out. The silver cations – positively charged molecules – come off and bind with the prominent negative charge on pathogens’ cell surfaces. This dynamic causes the destabilization of the cell membrane and a loss of the ability to replicate, which prevents bacterial reproduction via binary fission.2
When the silver is shrunken down, the ability for those cations to spontaneously come off actually increases, he explains. Furthermore, at that size range, it’s very easy for these particles to interact with the pathogens, which are huge at the nanoscale. As a result, the ability to specifically target and reach the organism is much greater.
“It is something that has been around for a very long time, and the safety has been looked at time and again,” he says. “No question there is always more to be done, especially when it comes to the environmental impact of silver,” he says, “but it is safe, and we know that it can be very helpful.” Ultimately, it allows wounds to cross the threshold and enter the proliferation phase of wound healing.
“This is not sci-fi and this is not something that’s coming down the road a couple of years from now. Silver dressings and nanosilver are already available,” he says. “In the right setting there’s no reason why we as dermatologists should not be using these when it’s appropriate.”
Silver nanoparticles visualized on transmission electron microscopy. Scale bar 100 nmAccording to Dr. Friedman, nanosilver can be combined with an antibiotic in order to prevent resistance and enhance activity. “You’re combing two things that have antibacterial properties, the silver being cidal, or killing, and the antibiotic being static, or inhibiting growth, so you hit it from both angles,” he says. “The likelihood of that organism developing resistance is limited because you’re attacking it from every side.”
Nanosilver and other antimicrobial nanomaterials such as gold, copper or carbohydrates, like chitosan, can be viewed as an opportunity to combine with dermatologists’ current armament, including antifungals and antibacterials, he says. Doing so can improve them and prevent a loss of potency.
While this is not yet common practice, Dr. Friedman says it is getting there and predicts that it eventually will be. “This is an obvious next step, especially given the medical crisis of epidemic proportions that is antimicrobial resistance,” he says.
Looking ahead, there are plenty of exciting developments that incorporate nanomaterials. “I think this is going to be a really major direction for the future in terms of how we manage wounds,” he adds, “and especially infected wounds.”
Disclosures: Dr. Friedman is on the consulting/ad boards of: Sanova works, Oakstone institute, Loreal, La Roche Posay, Galderma, Amgen, Onset, Aveeno, Valeant, Microcures, Nano Bio-Med, Biogen, Pfizer, Nerium, G&W Laboratories, Novartis, Occulus, Intraderm, Encore, Ferndale. He is a speaker for Amgen and Valeant, and received grants from Valeant.
1. International consensus. Appropriate use of silver dressings in wounds. An expert working
group consensus. London: Wounds International, 2012.
2. Chaloupka K, Malam Y, Seifalian AM. Nanosilver as a new generation of nanoproduct in biomedical applications. Trends Biotechnol. 2010;28(11):580-8.