Silver does more than kill bacteria

January 6, 2007

Friday 5 January 2007

Scientists in Hong Kong uncover the biological mechanism behind the age-old

treatment of wounds with silver.

Silver has for centuries been used to treat and prevent infection, and its

wound-healing properties are well known. Less well understood is exactly how the

metal acts as such an effective antimicrobial and healing agent. Kenneth Wong

and others at the University of Hong Kong recently investigated the

wound-healing properties of silver nanoparticles, and have shown that they do

more than simply kill bacteria.

Wounds heal following a complex combination of blood coagulation, tissue

inflammation and remodelling, and the best medical interventions are those that

prevent or at least minimise scarring. Silver has long been used to treat a

variety of diseases, and silver's antibacterial effect is thought to be due to

its penetration of cell walls and alteration of microbial DNA.

But the new research, published in the journal ChemMedChem (subscription

required), indicates that silver goes further than this and modifies cytokines -

the enzymes involved in cell growth and movement - leading to reduced

inflammation and an increased rate of healing.

Wong and his colleagues describe wounds treated with silver nanoparticles

healing in around 25 days, whereas it takes 29 days with common antibiotics, and

35 days with wounds left untreated. This translates into considerable cost

savings in medical care.

With a scale size of around 10 nanometres, Wong says that silver can be used in

a pure form and made into a stable solution, and also has the advantage that

with a large surface area, the dose can be reduced. " The next step is to

evaluate whether there is a receptor for silver, and what signalling pathways

are affected, " says Wong. " Furthermore, we are going to investigate if other

nano-metals or compounds can be applied in disease models such as haemostasis

and tissue regeneration. "

MIT-based medical scientist Rutledge Ellis-Behnke regards the Hong Kong group's

research as groundbreaking, saying: " Silver has been used for over a thousand

years in traditional Chinese medicine for wound healing, but this is the first

time that a hint of the true mechanism has been shown. "

Posted by Francis Sedgemore at 22:15 GMT

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