Oxygen plays a critical role the healing of wounds. Mapping oxygen levels in severe wounds and burns can help to significantly improve the success of surgeries to restore limbs and physical functions.
Inspired by a desire to help wounded soldiers, an international team of researchers led by Conor Evans of the Wellman Center for Photomedicine of Massachusetts General Hospital and Harvard Medical School have developed a paint-on, transparent, smart bandage that glows to indicate a wound's tissue oxygenation concentration, reports Science Daily.
"Information about tissue oxygenation is clinically relevant but is often inaccessible due to a lack of accurate or noninvasive measurements," explained lead author Zongxi Li, a research fellow on Evans' team.
The bandage's key ingredient is phosphors, a molecule that absorb light and then emits it via a process known as phosphorescence. "How brightly our phosphorescent molecules emit light depends on how much oxygen is present," said Li. "As the concentration of oxygen is reduced, the phosphors glow both longer and more brightly."
To make the bandage simple to interpret, the team incorporated a green oxygen-insensitive reference dye, so that changes in tissue oxygenation are displayed as a green-to-red color map.
The bandage is applied by painting it onto the skin's surface as a liquid, which dries to a solid film. Once the first layer has dried, a transparent barrier layer is then applied to protect the film and slow the rate of oxygen exchange between the bandage and the surrounding air, making the bandage sensitive to the oxygen within tissue.
Then a readout device provides a burst of excitation light that triggers the emission of the phosphors inside the bandage, and then it records the phosphors' emission. "Depending on the camera's configuration, we can measure either the brightness or color of the emitted light across the bandage or the change in brightness over time," Li said. "Both of these signals can be used to create an oxygenation map."
To improve the bandage, "we're developing brighter sensor molecules to improve the bandage's oxygen sensing efficiency," said Emmanuel Roussakis, a research fellow in Evans' laboratory and co-author, who is leading the sensor development effort.
The research was published in The Optical Society's journal Biomedical Optics Express.
