Smart Dressing Signals Wound Healing Status

The management of chronic wounds is a messy, bothersome affair. Dressings must be changed regularly for hygienic reasons and to examine the wound, take swabs and clean it. The process irritates the skin unnecessarily while providing a window for bacterial intrusion and infection. The ideal situation would be to leave the bandage on longer and have the nursing staff “read” the condition of the wound from outside.

Swiss researchers are now developing a smart wound dressing with integrated sensors to do just that. A portable, cheap and easy-to-use device for measuring fluorescence is capable of monitoring several wound status parameters at once. It should enable nursing staff to keep tabs on the pH as well as on glucose and oxygen levels while the wound heals. If these change, conclusions about other key biochemical processes involved in wound healing can be drawn.

If a wound heals normally, the pH rises to 8 before falling to 5 or 6. If a wound fails to close and becomes 

Using a UV lamp, the pH level in the wound can be verified without removing the bandage, allowing the healing process to continue unimpeded. (Image: Empa)chronic, however, the pH level fluctuates between 7 and 8. Therefore, it would be helpful if a signal on the bandage could inform the nursing staff that the wound pH is permanently high. On the other hand, if the bandage does not need changing for reasons of hygiene and pH levels are low, they could afford to wait.

If certain substances appear in the wound fluid, customized fluorescent sensor molecules respond by glowing or changing color in the visible or ultra-violet (UV) range. Thanks to a color scale, weaker and stronger changes in color can be detected and the quantity of the emitted substance be deduced.

The researchers designed a molecule composed of benzalkonium chloride, an antimicrobial ingredient in medical soap, and pyranine, a dye which glows under UV light. The biomarker performs well, especially at pH levels between 5.5 and 7.5. The colors can be visualized with simple UV lamps available in electronics stores.

The project Flusitex (Fluorescence sensing integrated into medical textiles) is being funded by the Swiss initiative Nano-Tera. Researchers from Empa teamed up with ETH Zurich, Centre Suisse d’Electronique et de Microtechnique (CSEM), and University Hospital Zurich for this research.