Engineers have created biohybrid chemical synapse, which is secreted by mesenchymal cells dopamine modulated the conductivity of the electrodes neuromorphic device. The mediator irreversibly changed the sensitivity of the postsynaptic unit and simulated long-term potentialy. Article published in the journal Nature Materias.
Biohybrids neuromorphic (created in the likeness of real neurons) synapses enables you to connect electronic devices with living cells. Usually in these interfaces the electrical activity of neurons recorded by the microelectrodes and modulated — because it has managed to reproduce such properties of synapses, both short – and long-term potencialu and synaptic weight. However, in living systems the relationship between cells and restructuring of the synapses is carried out in response to chemical signals from neurotransmitters. So, to simulate a living system, it is necessary to teach neuromorphic devices responsive to the rapid changes in chemical concentration.
Scientists from Italy and the United States under the leadership of Francesca Santoro (Santoro Francesca) from the Italian Institute of technology have created biohybrid synapse in which the presynaptic role playing module secreting dopamine cells (PC-12), and postsinapticescom domain is neuromorphic device. In living systems, dopamine plays an important role in synaptic plasticity and is associated with long-term potenciala and depression of synapses.
Neuromorphic module consists of electrodes made of polyethyleneoxide-polystyrenesulfonate: gate electrode and the channel. Electrical pulses in the first run the flow of ions in the electrolytic environment and affect the conductivity of the channel. When was the dopamine in the synaptic cleft, it is oxidized at the gate electrode, has changed its charge, resulting in a changed conductivity of the postsynaptic channel. The outflow of dopamine (in these synapses it is implemented by the reuptake neurotransmitter neurons) was performed using microfluidic the channel through which dopamine and its oxidation product was washed out of the artificial synapse.
Cells survived on the neuromorphic device and provide the dopamine for at least 24 hours. The width of the synaptic cleft (the distance between the cell membrane and postsynaptic electrodes) averaged 100 nanometers, and in places the most intimate contact is five to ten nanometers is close to the size of these synapses. The concentration of dopamine in the synapse biohybrids amounted to 10-15 micromol per liter.
The presence of dopamine caused irreversible changes in the base level of the postsynaptic channel conductance (synaptic weight) — so works long-term potentiate synapses. The conductivity change is dependent on cell density (the more dopamine they were allocated, the more noticeable was the effect) and the speed of the flow in the microfluidic channel, if dopamine was washed out too quickly, he did not have time to oxidize and conductivity change channels reversibles.