"Smart” Wound Dressings Could Identify and Destroy Infection-Causing Bacteria

A new study describes an innovative wound dressing system that releases an encapsulated antimicrobial agent only in the presence of pathogenic bacteria, allowing the body's normal microflora to continue providing a natural defense against infection.

Researchers at the University of Bath (United Kingdom) developed the prototype wound dressing, which is made of a nonwoven polypropylene fabric to which small vesicles containing an antibacterial agent are attached. When the pathogenic bacteria lyses the membranes of the vesicles attached to the smart fabric, they rupture, releasing the antibacterial agent and thus destroying the bacteria. By turning the virulence factors--toxins or enzymes that damage vesicle membranes--back onto the pathogens, the vesicle system can be thought of as a "Trojan horse,” inciting pathogenic bacteria to act as agents of their own destruction.


In their experiments, samples of a viable bacterial population of two species (Staphylococcus aureus and Pseudomonas aeruginosa) were tested every 20 minutes for four hours following exposure to the fabric. The researchers observed significant decreases in the concentrations of both species, and eventually nearly complete inhibition. The researchers also found that concentrations of P. aeruginosa declined at a faster rate than S. aureus, due to greater sensitivity of P. aeruginosa to the encapsulated antimicrobial agent.

The researchers also observed that in uninfected samples that contained only nonpathogenic Escherichia coli, concentrations of the E. coli were only slightly reduced, which likely resulted from minor leakage of the vesicles. By ensuring that the antibacterial agent is released only in the presence of pathogenic bacteria, the strategy minimizes evolutionary pressure for the selection of antibiotic-resistant bacteria, prolonging the effectiveness of the antibacterial agent. The study was published in the May 12, 2010, issue of the Journal of the American Chemical Society.

"The potential significance of this work is that we have a proof-of-principle of a ‘smart' system which is able to discriminate between pathogenic and nonpathogenic bacteria,” said study coauthor Toby Jenkins, Ph.D., of the department of biophysical chemistry. "The advantage of this in a wound dressing is that it will only release an antimicrobial if the wound becomes infected with dangerous bacteria, but won't respond to harmless commensal bacteria which may be present. This reduces the evolutionary selection pressure on bacteria of all types to evolve resistance and should slow the emergence of new antibiotic resistant species of bacteria such as MRSA.”

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