Artificial synapse that works with living cells created

Date:
June 15, 2020
Source:
Stanford University
Summary:
Researchers have created a device that can integrate and interact
with neuron-like cells. This could be an early step toward an
artificial synapse for use in brain-computer interfaces.



FULL STORY ==========================================================================
In 2017, Stanford University researchers presented a new device
that mimics the brain's efficient and low-energy neural learning
process. It was an artificial version of a synapse -- the gap across
which neurotransmitters travel to communicate between neurons -- made
from organic materials. In 2019, the researchers assembled nine of their artificial synapses together in an array, showing that they could be simultaneously programmed to mimic the parallel operation of the brain.


==========================================================================
Now, in a paper published June 15 in Nature Materials, they have tested
the first biohybrid version of their artificial synapse and demonstrated
that it can communicate with living cells. Future technologies stemming
from this device could function by responding directly to chemical
signals from the brain. The research was conducted in collaboration with researchers at Istituto Italiano di Tecnologia (Italian Institute of
Technology -- IIT) in Italy and at Eindhoven University of Technology (Netherlands).

"This paper really highlights the unique strength of the materials
that we use in being able to interact with living matter," said Alberto
Salleo, professor of materials science and engineering at Stanford and co-senior author of the paper. "The cells are happy sitting on the soft polymer. But the compatibility goes deeper: These materials work with
the same molecules neurons use naturally." While other brain-integrated devices require an electrical signal to detect and process the brain's messages, the communications between this device and living cells occur
through electrochemistry -- as though the material were just another
neuron receiving messages from its neighbor.

How neurons learn The biohybrid artificial synapse consists of two
soft polymer electrodes, separated by a trench filled with electrolyte
solution -- which plays the part of the synaptic cleft that separates communicating neurons in the brain. When living cells are placed on
top of one electrode, neurotransmitters that those cells release can
react with that electrode to produce ions. Those ions travel across the
trench to the second electrode and modulate the conductive state of this electrode. Some of that change is preserved, simulating the learning
process occurring in nature.



==========================================================================
"In a biological synapse, essentially everything is controlled by
chemical interactions at the synaptic junction. Whenever the cells
communicate with one another, they're using chemistry," said Scott Keene,
a graduate student at Stanford and co-lead author of the paper. "Being
able to interact with the brain's natural chemistry gives the device
added utility." This process mimics the same kind of learning seen in biological synapses, which is highly efficient in terms of energy because computing and memory storage happen in one action. In more traditional
computer systems, the data is processed first and then later moved
to storage.

To test their device, the researchers used rat neuroendocrine cells that release the neurotransmitter dopamine. Before they ran their experiment,
they were unsure how the dopamine would interact with their material --
but they saw a permanent change in the state of their device upon the
first reaction.

"We knew the reaction is irreversible, so it makes sense that it
would cause a permanent change in the device's conductive state," said
Keene. "But, it was hard to know whether we'd achieve the outcome we
predicted on paper until we saw it happen in the lab. That was when we
realized the potential this has for emulating the long-term learning
process of a synapse." A first step This biohybrid design is in such
early stages that the main focus of the current research was simply to
make it work.

"It's a demonstration that this communication melding chemistry and
electricity is possible," said Salleo. "You could say it's a first step
toward a brain- machine interface, but it's a tiny, tiny very first step."
Now that the researchers have successfully tested their design, they are figuring out the best paths for future research, which could include work
on brain-inspired computers, brain-machine interfaces, medical devices
or new research tools for neuroscience. Already, they are working on how
to make the device function better in more complex biological settings
that contain different kinds of cells and neurotransmitters.

This research was funded by the National Science Foundation, the
Semiconductor Research Corporation, a Stanford Graduate Fellowship, the
Knut and Alice Wallenberg Foundation for Postdoctoral Research at Stanford
and the European Union's Horizon 2020 Research and Innovation Programme.


========================================================================== Story Source: Materials provided by Stanford_University. Original written
by Taylor Kubota.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Keene, S.T., Lubrano, C., Kazemzadeh, S. et al. A biohybrid
synapse with
neurotransmitter-mediated plasticity. Nat. Mater., 2020 DOI:
10.1038/ s41563-020-0703-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200615115808.htm

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