Futuristic brain probe allows for wireless control of neurons
A study showed that scientists can wirelessly determine the path a
mouse walks with a press of a button. Researchers at the Washington
University School of Medicine, St. Louis, and University of Illinois,
Urbana-Champaign, created a remote controlled, next-generation tissue
implant that allows neuroscientists to inject drugs and shine lights on
neurons deep inside the brains of mice. The revolutionary device is
described online in the journal Cell. Its development was partially
funded by the National Institutes of Health.
“It unplugs a world of possibilities for scientists to learn how
brain circuits work in a more natural setting.” said Michael R.
Bruchas, Ph.D., associate professor of anesthesiology and neurobiology
at Washington University School of Medicine and a senior author of the
The Bruchas lab studies circuits that control a variety of
disorders including stress, depression, addiction, and pain. Typically,
scientists who study these circuits have to choose between injecting
drugs through bulky metal tubes and delivering lights through fiber
optic cables. Both options require surgery that can damage parts of the
brain and introduce experimental conditions that hinder animals’
To address these issues, Jae-Woong Jeong, Ph.D., a bioengineer
formerly at the University of Illinois at Urbana-Champaign, worked with
Jordan G. McCall, Ph.D., a graduate student in the Bruchas lab, to
construct a remote controlled, optofluidic implant. The device is made
out of soft materials that are a tenth the diameter of a human hair and
can simultaneously deliver drugs and lights.
“We used powerful nano-manufacturing strategies to fabricate an
implant that lets us penetrate deep inside the brain with minimal
damage,” said John A. Rogers, Ph.D., professor of materials science and
engineering, University of Illinois at Urbana-Champaign and a senior
author. “Ultra-miniaturized devices like this have tremendous potential
for science and medicine.”
With a thickness of 80 micrometers and a width of 500
micrometers, the optofluidic implant is thinner than the metal tubes,
or cannulas, scientists typically use to inject drugs. When the
scientists compared the implant with a typical cannula they found that
the implant damaged and displaced much less brain tissue.
The scientists tested the device’s drug delivery potential by
surgically placing it into the brains of mice. In some experiments,
they showed that they could precisely map circuits by using the implant
to inject viruses that label cells with genetic dyes. In other
experiments, they made mice walk in circles by injecting a drug that
mimics morphine into the ventral tegmental area (VTA), a region that
controls motivation and addiction.
The researchers also tested the device’s combined light and drug
delivery potential when they made mice that have light-sensitive VTA
neurons stay on one side of a cage by commanding the implant to shine
laser pulses on the cells. The mice lost the preference when the
scientists directed the device to simultaneously inject a drug that
blocks neuronal communication. In all of the experiments, the mice were
about three feet away from the command antenna.
“This is the kind of revolutionary tool development that
neuroscientists need to map out brain circuit activity,” said James
Gnadt, Ph.D., program director at the NIH’s National Institute of
Neurological Disorders and Stroke (NINDS). “It’s in line with the
goals of the NIH’s BRAIN Initiative.”
The researchers fabricated the implant using semi-conductor
computer chip manufacturing techniques. It has room for up to four
drugs and has four microscale inorganic light-emitting diodes. They
installed an expandable material at the bottom of the drug reservoirs
to control delivery. When the temperature on an electric heater beneath
the reservoir rose then the bottom rapidly expanded and pushed the
drug out into the brain.
“We tried at least 30 different prototypes before one finally worked,” said Dr. McCall.
“This was truly an interdisciplinary effort,” said Dr. Jeong, who
is now an assistant professor of electrical, computer, and energy
engineering at University of Colorado Boulder. “We tried to engineer
the implant to meet some of neurosciences greatest unmet needs.”
In the study, the scientists provide detailed instructions for manufacturing the implant.
“A tool is only good if it’s used,” said Dr. Bruchas. “We believe
an open, crowdsourcing approach to neuroscience is a great way to
understand normal and healthy brain circuitry.”