Intelligent Dressing Colorimetrically Detects Wound Pathogens

A prototype hydrogel wound dressing emits a fluorescent light when coming in contact with prevalent pathogens found within wound biofilms.

The dressing, developed by researchers at the University of Bath (United Kingdom) and Queen Victoria Hospital (QVH; East Grinstead, United Kingdom), is made of a hydrated agarose film in which vesicles containing the fluorescent dye were mixed with agarose and dispersed within the hydrogel matrix. Static and dynamic models of wound biofilm growth in clinical strains of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis were then established on a nanoporous polycarbonate membrane.

The dressing’s response to the different biofilms was then evaluated. The researchers found a clear fluorescent response within four hours of the initial inoculation of the biofilm, but for an established biofilm produced by a pathogenic strain, the response was within minutes. The sensitivity of the dressing to the biofilms was dependent on the species and strain types of the bacterial pathogens involved, but a relatively higher response was observed in strains considered good biofilm formers.

There was also a clear distinction in the levels of dressing response, wherein dressings that were tested on bacteria grown in biofilm or in planktonic cultures responded differently, suggesting that the level of expression of virulence factors is dependent on the growth mode. The researchers also demonstrated the efficacy of the wound dressing in an ex vivo porcine skin model of burn wound infection. The study was published in the October 22, 2015, issue of ACS Applied Materials & Interfaces.

“All wounds have some bacteria; whilst they are kept in check by immune clearance this is not a problem, but when bacteria start to form biofilms and critically colonize the wound, pathogenic changes can result,” said senior author Toby Jenkins, PhD, and colleagues. “The early detection of wound infection in situ can dramatically improve patient care pathways and clinical outcomes. Our dressing will measure this critical colonization point.”

A biofilm is any group of adherent microorganisms that are embedded within a self-produced matrix of extracellular polymeric substance (EPS), a conglomeration generally composed of extracellular DNA, proteins, and polysaccharides, which is also referred to as slime. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, which float or swim in a liquid medium.

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University of Bath
Queen Victoria Hospital