By disguising molecules with the tiniest of "hats," researchers have successfully stimulated the growth of blood vessels in mice just by shining a light through the skin. The findings were published in Nature Materials this week.
"Many biological processes involve complex cascades of reactions in which the timing must be very tightly controlled," Andrés García from Georgia Institute of Technology says in a news release. "Until now, we haven’t had control over the sequence of events in the response to implanted materials." And that’s because the immune system launches defensive attacks whenever materials are introduced into the body. So, why not disguise the drug or particle to sneak it in?
García and colleagues designed molecular "hats" for peptides—a compound that launches many of our biological processes—to cover the binding sites that cell receptors use to recognize them. When the team shines an ultraviolet light onto the peptides, this severs the link between the peptides and their hats. Once their disguises come off, the peptides’ true identities are revealed, and cells and other molecules begin interacting with them. “With this technique,” García adds, “we can deliver a drug or particle with its signal in the ‘off’ position, then use light to turn the signal ‘on’ precisely when needed.”
To test their sneaky light-activated technique, the team introduced disguised peptides on biomaterial made of water-based gel into mice through small cuts in their backs. Once the peptides were situated at the right place and the right time, the researchers simply shined a light through the skin, triggering cell adhesion and growth.
In one experiment, the team added a protein called vascular endothelial growth factor, which stimulates the growth of new blood vessels. Vascularization plays an important role in the healing process and in regenerative medicine. “We showed that if you keep the hat on, you get no vessel in-growth into the material,” García explains. “But if we turn on the light, we get growth of new blood vessels into the material.” Importantly, Science reports, when the light is shined after the clandestine implant has become interwoven with existing blood vessel networks, the mouse’s own blood supply would nourish the growing vessels with nutrients.
For the technique to work in humans, however, the researchers will need an alternative for UV light, which can’t penetrate very deeply into our much thicker skin and causes skin damage. They're currently looking into infrared light.