Here come the cyborgs. The electrical properties of specific types of nerve cell in living animals have been changed by genetically modifying them to produce conducting polymers on their surfaces.
The work, which promises to allow electrical control of specific groups of cells, could lead to everything from new treatments for conditions such as epilepsy to better ways of connecting prosthetic limbs to nerves, says Zhenan Bao of Stanford University in California. “Those are definitely possibilities,” she says.
At present, electrical implants such as those used for treating Parkinson’s disease often consist of metal electrodes pushed into the brain. One of the disadvantages is that there is no way to control the activity of specific types of neuron.
Bao and her colleagues genetically modified specific cell types to produce an enzyme on their surface that joins small molecules – monomers – together to make
a chain, or polymer. The polymer can be either an electrical conductor or insulator depending on the monomer.
The team did this first with animal and human cells in a dish, then with miniature human brain-like structures in the lab and finally in living nematode worms. The worms were first soaked in the monomers that the enzymes join to make the polymers. In larger animals, the monomers would need to be injected.
The researchers showed that this approach resulted in the targeted nerve cells becoming coated in the polymer, and that this altered the behaviour of the cells as they had expected it would. For instance, targeting the neurons that control movement made the worms less likely to move forward, or more likely to make sharp turns, depending on the type of polymer.
The researchers don’t yet understand why the modifications have these effects, says Bao. Nor have they yet attempted to connect to or interact with the modified neurons. But the results are proof of principle, she says. “It took many years.”
Journal reference: Science, DOI: 10.1126/science.aay4866
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