Nanosensor bandage measures wound oxygenation

Nanosensor bandage measures wound oxygenation

Published 4 June 2015

 

There is nothing new in the understanding that with combat come injuries, sometimes extreme injuries. In treating and healing wounds, however, physicians must overcome one obstacle which always challenges the healing of wounds: lack of oxygen. Thus, it is necessary to make certain that sufficient oxygen is reaching the healing wound. Chemists have developed a nanosensor bandage which measures the level of oxygen in wounds – a bandage which uses a changing color scheme to inform doctors of the level of oxygen supply in the treated wound.

There is nothing new in the understanding that with combat come injuries, sometimes extreme injuries. Military doctors, in particular surgeons, have done remarkable work in healing those wounds, often grafting healthy tissue, using microsurgery to connect blood vessel to the healthy tissue.
There is, however, one obstacle which always challenges the healing of wounds: lack of oxygen. Thus, it is necessary to make certain that sufficient oxygen is reaching the healing wound. Doctors often were unable to determine oxygen levels around the wound, and grafts have failed because of the difficulty in monitoring oxygenation.
Writing in the Scientific American, Mark Peplow reports a significant step forward.
Conor Evans is a chemist as the Harvard Medical School and the Wellman Center for Photomedicine at Massachusetts General Hospital. During a visit to the San Antonio Military Medical Center in Texas, he saw the problems resulting from the inability to monitor oxygen levels.
Evans and his colleagues began using dyes which react to different levels of oxygen, then added nano-sized molecules to regulate the dye’s activity. They then used these to create a liquid bandage which provides an indicator of the level of oxygen in a wound. The color scale used starts with green, indicating that plenty of oxygen is reaching, and gradually runs through yellow, orange, and red, indicating a worsening in the oxygenation level of the wound, announcing this status directly over the affected portion of the wound.
Evans’s technique consists of two dies mixed into a fast-drying liquid bandage which can be painted directly over a wound. A quick burst of blue light then energizes the dyes, one glowing bright green, the other bright red.
The presence of a sufficient supply of oxygen causes the red dye to become inactive, the bandage glowing a bright green. As fewer oxygen molecules are present in a specific area, however, the dyes then turn from yellow to orange, and finally to an attention-getting red.
Nanotechnology is the key to making all this work. Evens’s team then bonded the red dye molecules with a branching, 2-nanometer wide tree-like structure called a dendrimer. The result prevents molecules from interfering adjacent dye molecules, which would reduce their phosphorescence. They also block some oxygen molecules from reaching the dye. By starting with the lower levels producing a bright red, any changes are made more obvious.
Evans speculates that the bandage may also be engineered to dispense medications, a speculation Paula Hammond shares. Hammond, a chemist at the Massachusetts Institute of Technology, believes that nanotechnology would allow the creation of a bandage that could do so.
Hammond’s lab has found that applying bandages with nanoengineered coatings, it is possible slowly to release RNA or certain molecules to inhibit interfering RNAs, which can restrict the ability of genes that produce problem-causing proteins.
Evans’s bandages will begin human trials this year, while Hammond’s medication-delivery bandages have thus far been successful in animal experiments.
— Read more in Mark Peplow, “Nanotech Bandages Detect Health Trouble and Deliver Medicine,” Scientific American (1 April 2015)