Any fan of Star Trek knows that simply shine the light on a wound will heal many injuries in the future. Now scientists have put this future a little closer. In a new study, researchers have found a way to stimulate the growth of blood vessels, an important part of healing, striking the skin with ultraviolet light.
In the last decade, scientists have used light to manipulate the chemistry of the cells in a dish, but they are struggling to do the same in living organisms. "There are hundreds of different types of cells, you have many more other biological molecules," said Andrés García bioengineer at the Georgia Institute of Technology in Atlanta.
Then García and his colleagues turned to a water-based gel or hydrogel impregnated with a molecule called RGD peptide. The body uses this peptide to signal the cells to stick and grow into new tissue. The team then set another molecule of the RGD peptide to turn off. When the researchers shone UV light on the hydrogel, this molecular disguise filed and the RGD peptide became active.
The scientists then moved to animal testing. They made cuts on the backs of mice and implanted samples of hydrogel under their skins. They exposed hydrogel samples to UV light immediately after implantation, and others exposed, either 7 or 14 days later.
The cells grew just as well around the peptide samples impregnated, regardless of when they were irradiated, the reports online this week in team Nature Materials . When the RGD peptide is activated immediately after implantation, the mouse immune system recognizes as foreign and hydrogel surrounded by scar tissue. When the peptide was allowed to sleep for a few days before activation, however, the body's immune response was much lower and the hydrogel was better integrated into the mouse tissue.
SamplesResearchers then implanted hydrogel which, with the RGD peptide, was also impregnated with a protein known as vascular endothelial growth factor which stimulates the growth of new blood vessels. normal samples hydrogel triggered the growth of some blood vessels when implanted into mice. But the samples that have been impregnated with a growth factor of vascular endothelium and the RGD sequence in advance and then exposed to ultraviolet light after implantation had become interlaced with blood vessels networks, allowing clean mouse blood supply to send the blood through the hydrogel. This is important, García says, because if the tissue cultured in the laboratory is implanted in the body, it will not stay alive very long, unless it is supplied with nutrients by own blood supply of the animal.
One problem with the approach is that to remove the blocking group and activate the RGD peptide, the researchers had to use UV light, which does not deeply penetrate the skin of 0% light was absorbed by only the best of 0.5 mm from the skin of mice. The 10% that got through was still able to activate all the peptide. Although the process could be good enough in mice, it would have limited use in humans, which have thicker skin. Researchers are now trying to develop a process that will work with the infrared light, which penetrates human tissue much better. In principle, infrared light is also safer, as UV light can damage the skin and cause cancer (which is why you need sunscreen on the beach), although brief (10 minutes) l UV exposure used here caused no apparent damage mouse skin.
"It's very exciting," says bioengineer stem cell Matthias Lütolf of Technology Swiss Federal Institute of Lausanne. "It is the first demonstration that this concept really control biomaterials properties in the space and time by the light can be made to work in vivo. "He cautions, however, that although this study has provided evidence of important principle, researchers here simply stimulated blood vessels grow a time of their choice, they would have further increased if they had never caged the RGD peptide in the first place. the next step, he said, is to demonstrate that by controlling the time at which they turn on a molecular signal , researchers can process happens it will not happen otherwise. "All that is great in the human body is difficult to repair," he said, "because you get very quickly scarring. Now I wonder: Can we block the formation of scar tissue and inflammation and at some point the release of a signal while allowing healing "
bioengineer Jennifer Elisseeff Fellow of the Johns Hopkins University in Baltimore, Maryland, also found promising research?. She said that even with the limited penetration of UV light, the technology may already have uses. the ability to trigger the growth of blood vessels in the implant, while minimizing the body's inflammatory response, she said, could be used to produce glucose sensor that could be implanted directly into the body of diabetics and left, continuously monitor the sugar content of the blood flowing through them. More generally, she said, "it opens a door to really be able to handle the interaction of the body with these types of implants. I think we will begin to understand how primitive we really were. "
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