When researchers want to explore the brain of living animals, they have two options: surgically remove part of the skull, a procedure that can alter its function or trigger an immune response, or use CT or MRI scans, which isn't effective for visualizing activity of individual vessels or groups of neurons. But a new approach developed by Stanford chemists holds the promise of offering a third option that is non-invasive and captures "an unprecedented look at blood flowing through a living brain."
The technique involves injecting water-soluble carbon nanotubes into the subject's bloodstream, in this case mice, and using near-infrared light to illuminate the brain vasculature and track cerebral blood flow. The work, which was published in Nature Photonics, could be useful in advancing the study of stroke and migraines, as well as Alzheimer's and Parkinson's diseases. According to a recent Stanford Report story:
Amazingly, the technique allows scientists to view about three millimeters underneath the scalp and is fine enough to visualize blood coursing through single capillaries only a few microns across, said senior author Hongjie Dai, a professor of chemistry at Stanford. Furthermore, it does not appear to have any adverse affect on innate brain functions.
The technique could eventually be used in human clinical trials, Hong said, but will need to be tweaked. First, the light penetration depth needs to be increased to pass deep into the human brain. Second, injecting carbon nanotubes needs approval for clinical application; the scientists are currently investigating alternative fluorescent agents.
Previously: Lightning strikes twice: Optogenetics pioneer Karl Deisseroth’s newest technique renders tissues transparent, yet structurally intact, Peering into the brains of freestyle rappers to better understand creativity and Brain imaging, and the “image management” cells that make it possible