A Bandage of a Different Color

In 2010, a German team from the Fraunhofer Research Institutions for Microsystems and Solid State Technology EMFT created a bandage that looks like any other self-adhesive band-aid, but changes color to indicate infection by reacting to the pH of the skin beneath. Healthy healing wounds have a pH of about five or six. If this gets too alkaline, that can mean there’s an infection brewing underneath. The bandage will turn purple between 6.5 and 8.5 pH.

Another team from South Korea, Germany, and the US represented by Dr. Conor Evans from the Wellman Center for Photomedicine took a different tack: Liquid bandages funded in part by the Department of Defense. These can also clearly indicate wound healing, but not by detecting pH. The liquid bandage is designed to map oxygen concentrations in skin, including burns. In case you didn’t know, blood supply rich with oxygen and glucose is integral to wound healing. A deficit can result in poor recovery and chronic sores.

Current wound assessment is limited to the sniff test, visual inspection, or electrochemical analysis, which requires sticking electrodes (like needles) into the wound. The latter sounds like a miserable process for patients. A less invasive measurement option is available if you have the equipment to trace radioactive markers, but positron emission tomographs are pricey and not widely available.

The team’s new liquid bandage can deliver this information quickly and simply by changing color. Two oxygen-sensitive dyes; red porphyrin (similar to hemoglobin) and a green dye, are incorporated into a nitrocellulose liquid. The liquid glows green where the tissue underneath is properly oxygenated, and show red where there’s an oxygen deficit. A thin film on top of the bandage keeps atmospheric oxygen from confusing the readings, and the porphyrin from contacting the skin. The porphyrin is unique and the last component awaiting FDA approval; its brightness makes it possible to view the color changes with the naked eye. While porphyrins are generally expensive, this application only uses nanograms.

This new liquid is already being tested on animals, and the team is hoping to move forward to clinical trials soon. Dr. Conor Evans from the Wellman Center for Photomedicine called it a “platform technology that can be incorporated into existing bandages, or bioelectronic systems.”

Bio-Electronic Bandaids

A team of researchers from Tufts, Perdue, Harvard, and Women’s Hospital, supported by the National Science Foundation is, working on a new kind of bioelectronic smart bandage. The team introduced a bandage that uses sensors, biomaterials, and microsystems tech to monitor and treat wounds that require longer-term care, such as diabetic ulcers and burns.

Dubbed “flexible bioelectronics,” it’s still an emerging technology. The idea is to incorporate circuits into flexible, safe polymeric substrates. Intended for biomedical and life science applications, they will be able to track the healing process by checking oxygen levels and temperature. Health professionals would receive readings of this info, even – and especially – when they’re not with the patient.

They’re hard at work applying new materials like a hydrogel to improve the flexibility factor. For drug delivery; polymeric microparticles will be embedded in the hydrogel patch of the bandage during the manufacturing process. A stimulation mechanism goes on top of the patch. Flexible sensors monitor temp and pH, and if the wound changes for the worse, the researchers send a pulse to the stimulator to release the drugs in the microparticles.

A group of doctors from Melbourne and Monash Universities lead by Nico Voelcker is working on a flexible bandage that uses nanotechnology for monitoring and alerts. In theory, it will change color like the liquid bandages, and use sensors and Bluetooth to send data to a smartphone. The idea is to be able to detect the signs of infection sooner, and without removing the bandage and thereby compromising the healing process. The concept has been prototyped, but needs more funding to move on to clinical trials.

Preemptive care in bandaging

One team out of UC Berkeley, also supported by the NSF, is working on a bandage that detects tissue damage before it even becomes visible. Intended for pressure ulcers, otherwise known as bedsores, the bandage monitors the electrical changes caused by cell death. It is essentially a printed array of tiny electrodes on a thin flexible film. Bedsores can be anything but minor: Christopher Reeve died of an infection that started with a bedsore. When internal cells (not at the surface of the skin) start to die, the cell walls break down and the bandage reads the electrical signals that escape the degraded walls.

The sore-prevention bandage has already been tested on rats. Investigator of the study and Professor of surgery at USCF Dr. Michael Harrison said, “By the time you see signs of a bedsore on the surface of the skin it’s usually too late… If you can detect bedsores early on, the solution is easy. Just take the pressure off.”

Further indications for such bandages include using electrical fields to control the healing process. The theory is that since cells, epithelial cells in particular, are repsonsive to electical fields, manipulating such fields can change the way wounds heal. This is all in the future at this point, however if researchers can figure out how to trigger galvanotaxis — the process of cells migrating to the injury — it might be possible to adjust how a wound heals, minimizing scar tissue, for example, rather than just making it heal faster.

The two NSF and the DoD project conclude in 2016, but we shouldn’t expect to see the next generation of bandages on our shelves for at least another five years. Some of the technologies listed here involve disciplines that don’t always coordinate. After speaking to some of the doctors involed with the technology in this article, we can hope that Digital Trends has served some small purpose by encouraging chemists and bio-electronics specialists to come together.

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