Inspired by a desire to help wounded soldiers, an international multidisciplinary team of researchers has created a paint-on, see-through smart bandage that glows to indicate the concentration of oxygenation in a wounds tissue, according to a news release.
Because oxygen plays a critical role in healing, mapping these levels in severe wounds and burns can help to significantly improve the success of surgeries to restore limbs and physical functions. The team of researchers from the U.S., Germany and South Korea, led by Conor L. Evans, PhD, an assistant professor at the Wellman Center for Photomedicine of Massachusetts General Hospital and Harvard Medical School in Boston, published its findings Oct. 1 in The Optical Societys open-access journal Biomedical Optics Express.
Information about tissue oxygenation is clinically relevant but is often inaccessible due to a lack of accurate or noninvasive measurements, lead author Zongxi Li, PhD, an HMS research fellow on Evans team, said in the release.
The teams bandage provides direct, noninvasive measurement of tissue oxygenation by combining three compact and inexpensive components: a bright sensor molecule with a long phosphorescence lifetime and appropriate dynamic range; a bandage material compatible with the sensor molecule that conforms to the skins surface to form an airtight seal; and an imaging device capable of capturing the oxygen-dependent signals from the bandage.
This work is part of the teams long-term program to design a Sensing, Monitoring And Release of Therapeutics bandage to improve care for patients with chronic or acute wounds, senior author Evans said in the release. A big part of the bandage is phosphors molecules that absorb light and then emit it via a process known as phosphorescence.
How brightly our phosphorescent molecules emit light depends on how much oxygen is present, Li said in the release. As the concentration of oxygen is reduced, the phosphors glow both longer and more brightly.
To make the bandage simple to interpret, the team also incorporated a green oxygen-insensitive reference dye, so changes in tissue oxygenation are displayed as a green-to-red colormap.
The bandage is painted onto the skins surface as a viscous liquid, which dries to a solid, thin film within a minute. Once the first layer has dried, a transparent barrier layer is applied to protect the film and slow the rate of oxygen exchange between the bandage and room air making the bandage sensitive to the oxygen within the tissue.
The final piece involves a camera-based readout device, which performs two functions. It provides a burst of light that triggers the emission of the phosphors inside the bandage, and then it records the phosphors emission.
Depending on the cameras 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 in the release. Both of these signals can be used to create an oxygenation map.
The emitted light from the bandage is bright enough that it can be acquired using a regular camera or smartphone making a portable, field-ready device possible. Immediate uses for the bandage include monitoring patients at risk of developing ischemic conditions, postoperative monitoring of skin grafts or flaps and burn-depth determination as a guide for surgical debridement.
The need for a reliable, accurate and easy-to-use method of rapid assessment of blood flow to the skin for patients remains a clinical necessity, co-author Samuel Lin, MD, FACS, an HMS associate professor of surgery at Beth Israel Deaconess Medical Center in Boston, said in the release. Plastic surgeons continuously monitor the state of blood flow to the skin, so the liquid-bandage oxygenation sensor is an exciting step toward improving patient care within the realm of vascular blood flow examination of the skin.
The team is working to develop brighter sensor molecules so the bandage is more efficient at sensing oxygen, according to Emmanuel Roussakis, PhD, a research fellow and co-author who is leading the sensor development effort. The team also hopes to expand the sensing capability of the bandage to other treatment-related parameters such as pH, bacterial load, oxidative states and specific disease markers. Another goal is to incorporate an on-demand drug release capacity.
In the future, our goal for the bandage is to incorporate therapeutic release capabilities that allow for on-demand drug administration at a desired location, Evans said in the release. It allows for the visual assessment of the wound bed, so treatment-related wound parameters are readily accessible without the need for bandage removal preventing unnecessary wound disruption and reducing the chance for bacterial infection.
The research was supported by the Military Medical Photonics Program from the U.S. Department of Defense and National Institutes of Health.