Gel shines bright to spot bacteria

U. SHEFFIELD (UK) — Polymers that light up in the presence of bacteria could offer a new way to quickly detect infected wounds.

Polymers are irreversibly attached to fragments of antibiotics, which bind to either gram negative or gram positive bacteria—both of which cause serious infections.

When contained in a gel and applied to a wound, the infection’s severity can be detected by the level of fluorescence, helping clinicians decide whether or not to use antibiotics, and the most appropriate type of antibiotic treatment to prescribe.

The same gels can also be used to remove bacteria from infected wounds in tissue engineered human skin.

“The polymers incorporate a fluorescent dye and are engineered to recognize and attach to bacteria, collapsing around them as they do so,” says Sheila MacNeil, a professor at the University of Sheffield and an expert in tissue engineering and wound healing. “This change in polymer shape generates a fluorescent signal that we’ve been able to detect using a hand-held UV lamp.”

The new technology could ultimately reduce the detection of bacterial infection to within a few hours, or even less.

“The availability of these gels would help clinicians and wound care nurses to make rapid, informed decisions about wound management, and help reduce the overuse of antibiotics,” adds project lead Steve Rimmer.

Currently, determining significant levels of bacterial infection involves swabbing the wound and culturing the swabs in a specialist bacteriology laboratory with results taking several days to be available.

The research has already demonstrated that the polymer (PNIPAM), modified with an antibiotic (vancomycin) and containing a fluorescent dye (ethidium bromide), shows a clear fluorescent signal when it encounters gram negative bacteria. Other polymers have been shown to respond to S. aureus, a gram positive bacteria.

The findings indicate a hand-held sensor device can now be developed for use in a clinical setting.

The scientists are also investigating whether using a sophisticated technique called fluorescence Non Radiative Energy Transfer (NRET) to generate the light signal could enable a highly refined sensor technology that could have applications in other areas.

“For example, we think that NRET could be very useful in an anti-terrorist and public health capacity, detecting pathogen release or bacterial contamination, whether accidental or deliberate,” Rimmer says.

“NRET also allows us to learn more about how the polymers collapse around the bacteria, which is important in developing our understanding of how bacteria interact with these novel responsive polymers.”

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