Highly realistic artificial nerve cells

Researchers at Linköping University (LiU) in Sweden have created an artificial organic neuron that closely mimics the characteristics of
biological nerve cells.
This artificial neuron, which stimulates natural nerves, is a promising technology that has promising applications in various medical treatments in the future
.

The Laboratory of Organic Electronics (LOE) continues to work on the development of increasingly powerful artificial nerve cells
.
In 2022, a team of scientists led by Associate Professor Simone Fabiano demonstrated how artificial organic neurons can be integrated into living carnivorous plants to control the opening and closing
of their mouths.
This synthetic nerve cell has 2 of 20 characteristics that differ from biological nerve cells
.

In their latest study, published in the journal Nature Materials, researchers at Liu University developed a new artificial nerve cell called "conductance-based organic electrochemical neurons," or c-OECN, that closely mimics 15 of the 20 neural features of biological nerve cells, making them function more closely like natural nerve cells
.

"One of the key challenges in creating artificial neurons that effectively mimic real biological neurons is the ability to
bind ion modulation.
Traditional artificial neurons made of silicon can mimic many nerve functions, but cannot communicate
through ions.
In contrast, c-OECNs use ions to exhibit several key features of truly biological neurons," said
Simone Fabiano, principal investigator in the LOE Organic Nanoelectronics Group.

In 2018, this research group at Linköping University was one of the first to develop organic electrochemical transistors based on n-type conductive polymers, a material
that can conduct a negative charge.
This makes it possible
to build printable complementary organic electrochemical circuits.
Since then, the group has worked to optimize these transistors so that they can be printed on thin plastic foil on a printing press
.
As a result, it is now possible to print thousands of transistors on flexible substrates and use them to develop artificial nerve cells
.

In the newly developed artificial neurons, ions are used to control the flow of electrons through an n-type conductive polymer, causing a spike
in the device's voltage.
This process is similar
to that found in biological nerve cells.
The unique material in artificial nerve cells also allows the current to increase and decrease in an almost perfect bell-shaped curve, similar to the activation and inactivation
of sodium ion channels found in biology.

"Several other polymers also exhibit this behavior, but only rigid polymers that are elastic to disorder can make the device run stably
," says Simone Fabiano.

In experiments conducted in collaboration with the Karolinska Institute (KI), new c-OECN neurons were attached to
the vagus nerve of mice.
The results showed that artificial neurons could stimulate nerves in mice, causing them to change their heart rate by 4.
5 percent
.
The fact that artificial neurons are able to stimulate the vagus nerve itself in the long term paves the way
for basic applications of various forms of medical treatment.
In general, organic semiconductors have the advantages of biocompatibility, softness and ductility, while the vagus nerve plays a key role
in the body's immune system and metabolism.

The researchers' next step will be to reduce the energy consumption of artificial neurons, which is still much higher than that of human nerve cells
.
There is still a lot of work to be done to artificially replicate nature
.

"There's still a lot we don't fully understand about the human brain and nerve cells
.
In fact, we don't know how nerve cells use many of these 15 traits
.
Simulating nerve cells allows us to better understand the brain and build circuits
capable of performing intelligent tasks.
We still have a long way to go, but this study is a good start," said
Padinhare Cholakkal Harikesh, a postdoc and lead author of the scientific paper.

Padinhare Cholakkal Harikesh, Chi-Yuan Yang, Han-Yan Wu, Silan Zhang, Mary J.
Donahue, April S.
Caravaca, Jun-Da Huang, Peder S.
Olofsson, Magnus Berggren, Deyu Tu, Simone Fabiano.
Ion-tunable antiambipolarity in mixed ion– electron conducting polymers enables biorealistic organic electrochemical neurons.
Nature Materials, 2023