Champaign, IL--Researchers at the University of Illinois (U. of I.) at Urbana-Champaign and Washington University (St. Louis, MO) have developed a new class of tiny, injectable light-emitting diodes (LEDs) (http://www.laserfocusworld.com/articles/2001/12/ksu-researchers-fabricate-blue-micro-leds.html) the size of individual neurons that are lighting the way for neuroscientists in the field of optogenetics (http://www.laserfocusworld.com/articles/2011/01/optogenetics-turning-light-bulbs-on-in-the-brain.html) and beyond. Led by John A. Rogers, the Swanlund professor of materials science and engineering at the U. of I., and Michael R. Bruchas, a professor of anesthesiology at Washington University, the researchers will publish their work in the April 12 issue of Science.
"These materials and device structures open up new ways to integrate semiconductor components directly into the brain," said Rogers, who directs the Frederick Seitz Materials Research Laboratory at the U. of I. "More generally, the ideas establish a paradigm for delivering sophisticated forms of electronics into the body: ultra-miniaturized devices that are injected into and provide direct interaction with the depths of the tissue."
The researchers demonstrated the first application of their devices in optogenetics (http://www.laserfocusworld.com/articles/2012/11/3d-optogenetics-probe-mit.html), a new area of neuroscience that uses light to stimulate targeted neural pathways in the brain. The procedure involves genetically programming specific neurons to respond to light. Optogenetics experiments (http://www.bioopticsworld.com/articles/print/volume-4/issue-3/features/neurology-light-tissue-interaction-in-vivo-precision-targeting-with-optogenetics.html) with mice illustrate the ability to train complex behaviors without physical reward, and to alleviate certain anxiety responses. Yet fundamental insights into the structure and function of the brain that emerge from such studies could have implications for treatment of Alzheimer's (http://www.laserfocusworld.com/articles/print/volume-45/issue-8/columns/in-my-view/a-healthy-future-for-optogenetics.html), Parkinson's, depression, anxiety and other neurological disorders.
While a number of important neural pathways now can be studied by optogenetics, researchers continue to struggle with the engineering challenge of delivering light to precise regions deep within the brain. The most widely used methods tether the animals to lasers with fiber-optic cables embedded in the skull and brain--an invasive procedure that also limits movements, affects natural behaviors and prevents study of social interactions.
The newly developed technologies bypass these limitations with specially designed powerful LEDs that are injected into the brain to provide direct illumination and precise control. The devices are printed onto the tip end of a thin, flexible plastic ribbon--thinner than a human hair and narrower than the eye of a needle--that can insert deep into the brain with very little stress to tissue. The active devices include not only LEDs but also various sensors and electrodes that are delivered into the brain with a thin, releasable micro-injection needle. The ribbon connects the devices to a wireless antenna and a rectifier circuit that harvests radio frequency energy to power the devices. This module mounts on top of the head and can be unplugged from the ribbon when not in use.
The complete device platform includes LEDs, temperature and light sensors, microscale heaters, and electrodes that can both stimulate and record electrical activity. These components enable many other important functions--for example, researchers can measure the electrical activity that results from light stimulation, giving additional insight into complex neural circuits and interactions within the brain.
SOURCE: University of Illinois at Urbana-Champaign; http://news.illinois.edu/news/13/0411optogenetics_JohnRogers.html