Nanocellulose wound dressing changes colour to indicate infection

The dressing, described in Materials Today Bio, has been developed by researchers at Linköping University in collaboration with colleagues at Örebro and Luleå Universities, Sweden.

“Being able to see instantly whether a wound has become infected, without having to lift the dressing, opens up for a new type of wound care that can lead to more efficient care and improve life for patients with hard-to-heal wounds,” said Daniel Aili, professor in the department of Biophysics and Bioengineering at Linköping University. “It can also reduce unnecessary use of antibiotics.”

The dressing is made of tight mesh nanocellulose that prevents ingress of bacteria and other microbes. The material simultaneously lets gases and liquid through, which is important to wound healing. Once applied, the dressing is intended to stay on during the entire healing process. Should the wound become infected, the dressing will show a colour shift.

Non-infected wounds have a pH value of about 5.5 but when an infection occurs the wound becomes increasingly basic and may have a pH value of 8 or higher because bacteria in the wound change their surroundings to fit their optimal growth environment. An elevated pH value in the wound can be detected long before any pus, soreness or redness, which are the most common signs of infection.

To make the wound dressing show the elevated pH value, the researchers used bromthymol blue (BTB), a dye that changes from yellow to blue when the pH value exceeds 7. For BTB to be used in the dressing without being compromised, it was loaded onto a silica material with nanometre-sized pores. The silica material could then be combined with the dressing material without compromising the nanocellulose.

Wound infections are often treated with antibiotics that spread throughout the body, but if the infection is detected at an early stage, local treatment may be suitable. To this end, Aili and colleagues at Örebro University are also developing anti-microbial substances based on so-called lipopeptides that kill off all types of bacteria.

“The use of antibiotics makes infections increasingly problematic, as multi-resistant bacteria are becoming more common. If we can combine the anti-microbial substance with the dressing, we minimise the risk of infection and reduce the overuse of antibiotics,” said Aili.

Aili added that the new wound dressing and the anti-microbial substance are part of a programme to develop a new type of wound treatment in out-patient care.

Both studies are part of the HEALiX research project financed by the Swedish Foundation for Strategic Research with the objective of developing a new type of wound treatment.