An international research team led by Francesca Santoro from Jülich has developed a biochip that mimics the human retina. The innovation is part of a broader effort in bioelectronics to repair dysfunction in the body and brain. The chip is the result of a collaboration involving experts from the Jülich Research Center, RWTH Aachen University, the Italian Institute of Technology and the University of Naples. Their work and research results have been published in the journal Nature Communications.
The fusion of man and machine is the epitome of science fiction. In real life, people have already taken the first steps towards realizing such cyborgs: pacemakers can treat arrhythmias, cochlear implants can improve hearing, and retinal implants can at least help nearly blind people see a little. In the future, a new type of chip could help retinal implants better integrate with the human body. It is based on conductive polymers and light-sensitive molecules and can be used to mimic the retina and visual pathways. It was developed by Francesca Santoro's research group at the Jülich Institute of Bioelectronics (IBI-3) in collaboration with RWTH Aachen University, the Italian Institute of Technology in Genoa and the University of Naples.
"Our organic semiconductor is able to recognize the intensity of light falling on it. Something similar happens in our eyes," explains Santoro, professor of neuroelectronic interfaces at RWTH Aachen University and visiting researcher at the Italian Institute of Technology. "The amount of light that strikes the individual photoreceptors ultimately forms an image in the brain."
This new type of semiconductor is unique in that it is composed entirely of non-toxic organic components and is flexible to work with ions, which are charged atoms or molecules. Therefore, it can be better integrated into biological systems than traditional silicon semiconductor components, which are rigid and only work with electrons. The researchers explain: "Our body cells specialize in using ions to control certain processes and exchange information. However, so far this development is only a 'proof of concept'. The material was synthesized and then characterized, but we were able to show that the typical properties of the retina can be mimicked with it."
The researchers are already considering another possible application: Since exposure to light changes the conductivity of the polymer used in both the short and long term, the chip could also function as an artificial synapse. Real synapses work in a similar way: By passing electrical signals, they change their size and efficiency, which is what underlies our brain's ability to learn and remember, for example. "In future experiments, we hope to combine these components with biological cells and connect many individual biological cells together," Santoro said.
In addition to artificial retinas, Santoro's team is developing other approaches to bioelectronic chips that can interact in a similar way with cells in the human body, specifically the nervous system. "On the one hand, we were trying to replicate the three-dimensional structure of nerve cells, and on the other hand, we were also trying to replicate their functions, such as processing and storing information. It turned out that the biopolymers they used in the artificial retina were a suitable starting material. We could use them to replicate the branching structure of human nerve cells, as well as their many dendrites. You can imagine it being a bit like a tree," the scientist explains. This is important because real cells prefer this branch-like three-dimensional structure to smooth surfaces, allowing them to establish close connections with artificial cells.
First, different biochips can be used to study real neurons, i.e. cellular communication. Second, Santoro and her team hope to one day use their components to actively intervene in cells' communication pathways to trigger certain effects. For example, what Santoro has in mind here is correcting errors in information processing and transmission that occur in neurodegenerative diseases such as Parkinson's or Alzheimer's disease, or supporting organs that no longer function properly. Furthermore, such elements could also serve as interfaces between prosthetic limbs or joints.
Computer technology can also benefit. Due to its properties, this chip is destined to become hardware for artificial neural networks. Until now, artificial intelligence programs still use classic processors that cannot adjust their structure. They just use complex software to imitate and change the self-learning operating principle of neural networks. This is very inefficient. Artificial neurons could make up for this shortcoming: they would enable computer technology to mimic the way the brain works at every level.