Applied
onto the business end of artificial skin, nanofilms that release
antibacterial silver over time can eradicate bacteria in full-thickness
skin wounds in mice.
Pioneered
by a multidisciplinary team of researchers from the University of
Wisconsin-Madison, University of Colorado-Denver, and University of
California, Davis, such antibacterial wound dressings someday could
benefit millions of people worldwide who suffer from serious burns or
chronic wounds.
The team described its results in a paper published in the August 2012 issue of the journal Annals of Surgery.
In
the United States, some seven million people suffer from chronic wounds
or serious burns. Their journey to recovery often is plodding, and
pockmarked with setbacks, prolonged excruciating pain, and an
ever-present risk of infection. Many of these people endure multiple
daily dressing changes during which nurses clean their wounds and cover
them with gauze soaked in antimicrobial agents to ward off infection.
Approximately
20% of patients develop infection in their wounds. And infected,
difficult-to-heal wounds such as diabetic foot ulcers can lead to
amputation, says Dr. Michael Schurr, a corresponding author on the
paper. “The real question is bacteria in wounds,” says Schurr, formerly a
clinician and professor of surgery at UW-Madison and now a professor of
surgery in the University of Colorado School of Medicine. “If you take
an antibiotic pill, the antibiotics circulate through your body but
don’t really contact the surface of your skin. That’s why we’re heading
to antibacterial dressings.”
Applied
to wounds or burns, artificial skin promotes wound healing and reduces
the discomfort associated with wound care. Also known as a biologic
dressing, artificial skin consists of two layers: The bottom layer
contacts the wound and contains biological compounds that encourage new
skin cells to grow, while the top layer acts like a protective covering
until the wound heals.
While
antimicrobial agents help kill infection-causing bacteria, high
concentrations of antimicrobial agents are toxic to the biological
components in artificial skin, slowing the healing process.
Silver
is effective as an antimicrobial agent-even against drug-resistant
bacteria. However, until now, it has not been possible to incorporate
silver into artificial skin because traditional methods, such as
dip-coating, are too harsh on the delicate biological components in
artificial skin, says Ankit Agarwal, a UW-Madison honorary research
associate in chemical and biological engineering and co-lead author of
the paper. “The industry has been looking for new methods,” he says.
Working
with Nicholas Abbott, the John T. and Magdalen L. Sobota professor of
chemical and biological engineering at UW-Madison, Agarwal developed
polymer nanofilms that contain precise amounts of silver nanoparticles
that release over 10 days. With inspiration from techniques used in the
electronics industry, the researchers also devised an ingenious method
for “stamping” the nanofilms onto the soft bottom layer of commercially
available artificial skin. “A lot of wound dressings are very
specialized,” says Schurr. “One of the advantages of the nanofilms is
that they don’t change the properties of the dressings.”
The
nanofilms do, however, eradicate bacteria. Agarwal and Kathleen
Guthrie, a postgraduate trainee in the School of Veterinary Medicine at
UW-Madison, tested the artificial skin in mice with full-thickness skin
wounds, or those in which all layers of skin are removed. They added
bacteria to the wounds and applied artificial skin with and without the
silver nanofilms. After just three days, wounds dressed artificial skin
resulted in persistent infections, while wounds with the silver-modified
artificial skin contained significantly less bacteria.
It’s
research that supports results of the team’s prior laboratory-based
studies. Now, in partnership with companies that manufacture artificial
skin, the team will work toward clinical trials, as well as identifying
specific areas-for example, dressings for burn victims who are
children-where antimicrobial wound dressings can make the biggest
impact. “The whole point here is to improve the care of people with
medical problems and this partnering process is very important,” says
Schurr.
Source: University of Wisconsin-Madison
