Friday September 16 2011
The system causes glowing when bacteria are present
Scientists are developing a “glowing bandage to treat infection”, The Guardian has today reported. The news is based on a new technique devised by researchers at the University of Sheffield, who are currently developing visual methods for quickly identifying the presence of bacteria that could infect a wound.
Their technique involves using a long chain-shaped molecule (a polymer) bound to an antibiotic and to a fluorescent dye. In lab models of wounds the fluorescent dye would begin to glow under an ultraviolet (UV) lamp if the antibiotic bound to bacteria. This happens because, under these circumstances, the special polymer changes shape. The researchers hope to use the discovery to develop a gel that can be inserted into wounds to detect bacteria.
So far the technique has only been tested in an engineered model of skin tissue and requires further development, but it does appear to have a great deal of potential. Leader of the project, Dr Steve Rimmer, is quoted by The Daily Telegraph as saying “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”. At present, clinical techniques can take several days to identify the presence and type of bacteria in a wound.
What is the basis for these current reports?
These reports come following a presentation of new research at the British Science Festival in Bradford. Professor Sheila MacNeil of the University of Sheffield presented a talk at the event entitled ‘Shining a light on bacteria - developing a novel sensor for bacteria’.
In her address Professor MacNeil described how over the past five years her team of researchers, led by Dr Steve Rimmer of the university’s Department of Chemistry, has been developing a substance that can bind to bacteria and emit a fluorescent signal when it does so. During the presentation and in supporting press releases the team presented some of the potential applications for their new substance. This new substance is a polymer, which is a chain of identical, repeating chemical substances that can extend indefinitely.
The project received funding from the Engineering and Physical Science Research Council (EPSRC) and the Defence Science and Technology Laboratory (Dstl), an agency of the Ministry of Defence.
What is the new development?
Using an engineered model of skin tissue the researchers found that when their polymer (PNIPAM) was bound to an antibiotic, the binding of the antibiotic to bacteria would cause the polymer to change shape. Given this shape-changing property, the researchers set themselves the task of incorporating the polymer into a new light-based method for sensing bacterial infection. They hoped this might provide a visual way to detect infections that would currently need to be confirmed through lengthy lab techniques.
To achieve this goal they adapted a technique called ‘fluorescence non-radiative energy transfer (NRET)’. A clear fluorescent signal would be given when their polymer changed shape, which would be detectable when placed under a UV lamp. In instances when there were no bacteria for the antibiotic to bind to then no shape change would occur and no fluorescent glow would be seen under the UV lamp. The antibiotic that was bound to the polymer was vancomycin, which is a very strong antibiotic that is potent against bacteria resistant to other antibiotics, and usually reserved for the treatment of serious bowel or blood infections.
How could the new technology be used?
Professor MacNeil says there could be widespread applications for their new technique. In theory, the new technology would give doctors an easier and quicker way to identify and initiate the treatment of infected wounds. Current methods of identifying when an infection is present involve taking swabs from the site of a wound or injury and then culturing them in the laboratory to see whether bacteria grow from the sample. If bacteria are found, the type of bacteria directs doctors to the most appropriate antibiotic to use. With current clinical techniques the process of growing and identifying these bacteria can often take several days.
The researchers describe that the new technology could be of benefit to the healthcare profession in general, as well as those involved in detecting infection in battlefield conditions, where specialist laboratory facilities may not be so readily available.
What stage is the research at?
The new technology is currently described as showing ‘proof of concept’. This means that the premise behind using the technique has been shown to be sound. However, Professor MacNeil says that work is ongoing to produce a detector system that is of clinical use.
The team’s ongoing aim is to produce a polymer gel that could be placed on a wound and allow detection of infection and, within an hour, give an indication of the amount of bacteria present using a hand-held UV lamp. The researchers also say that it is possible that through the use of polymers doctors would also be able to determine what group the bacteria belonged to, guiding decisions about the appropriate use of antibiotics and further management.
What are the implications of the current research?
Based on the limited information available from the abstract and press releases it is not possible to appraise this technique in more depth. So far the technique has only been reported to be tested in engineered tissue models in the laboratory and, though it appears to have potential, the technique is still undergoing further development. Once developed it would then need safety and efficacy testing in studies of people with actual wounds. It is not clear at the current time what sort of wounds this dressing could be applied to, for example, whether it would be appropriate to apply to acute wounds, such as cuts or burns, or to chronic lesions such as ulcers (for example pressure ulcers, diabetic ulcers, venous or arterial ulcers).
In its current form the technique would only detect bacteria, but not the non-bacterial organisms that can infect wounds, such as viruses, fungi and protozoa. It is also not possible to say from the current presentation how the technique would be incorporated into the many conventional procedures involved in the management of different types of wounds and wound infections. Current wound and wound infection management is highly variable depending on the type of wound. It can include inspection of the wound for classical signs of infection (such as redness, swelling and discharge), taking swabs to establish sensitivity to antibiotics or other antimicrobials, wound cleaning (for example surgical cleaning and removal of infected tissue [debridement], or maggot therapy), and use of appropriate dressings (which may contain antiseptic items such as silver and iodine).
The technique also raises other questions, particularly that of antibiotic resistance. The researchers state that one of their aims is to prevent the overuse of antibiotics through having a dressing that can detect wound contamination at an early stage. However, the current research only describes the use of vancomycin, and it is unclear if other antibiotics have been tested. Vancomycin is a highly potent antibiotic, normally reserved for severe infections that cannot be treated with other antibiotics. If it were to be combined in a wound dressing and then widely used, there is a possibility that this could increase the chance of bacteria developing resistance against this important antibiotic.
Further developments from this interesting research are awaited.