Bio-inspired technology could one day lead to a bionic eye

A new design for eye and brain implants takes its inspiration from nature.

UO researchers have grown rodent retinal neurons on fractal-patterned electrodes, which mimic the repetitive branching pattern in which neurons naturally grow. It’s one step closer to creating a bio-inspired bionic eye, an old goal for UO physicist Richard Taylor.

Taylor hopes that tiny electrodes may someday be implanted into the eye to restore vision in people with macular degeneration or other vision disorders.

The new work provides experimental evidence that his team has been pursuing for years, that neurons, which are themselves fractals, will connect better to a fractal-patterned electrode than they do to a conventionally shaped electrode. , thereby allowing better signal transmission between the implants. and brain.

Taylor and his colleagues report their findings in a paper published in PLOS ONE.

“I’m very excited because this paper is three years of data exploring what happens when these retinal cells interact with fractal electrodes,” he said.

Nerve implants hold the glimmer of the future, but they are already being used to help people with conditions ranging from Parkinson’s disease to spinal cord injury. A chip that stimulates a particular location within the brain could help reduce tremors or even restore the ability to walk, speak or see.

In order to successfully send signals to the brain or eye, an implanted electrode must be able to connect to a network of existing neurons. Neurons naturally grow in a tree-like fractal pattern, which always leads to better branching.

Most electronics are not shaped like that; They are designed for use inside machines, not living things. Instead, Taylor wondered, why not convince neurons to attach electrodes in a pattern that suited their instincts?

“You want neurons to engage in order to be stimulated; that’s the ultimate goal in designing any electrode,” said Saba Moslehi, a postdoctoral researcher in Taylor’s lab. So they have a greater tendency to interact than objects with completely different characteristics.”

Taylor, a physicist specializing in fractals, presented the idea for a life science research competition in 2014. To his surprise, it surpassed nearly a thousand competing pictures. And since then, with the help of UO professors Benjamin Allemann and Chris Neal from Lund University in Sweden and colleagues, his group has been exploring its potential.

In previous studies, they performed computer simulations that suggested fractal-patterned electrodes would be more effective than conventional electrode shapes. Then, to test the idea experimentally, the Yuo team used electrodes made of smooth silicon chips with branches made of carbon nanotubes patterned on the chip surface.

Neurons like to attach to textured nanotubes, so researchers can control where neurons attach to electrodes by modifying the nanotube map on its surface.

Mosley, along with doctoral students Conor Rowland and Julian Smith, used facilities at UO’s Center for Advanced Materials Characterization in Oregon to create silicon-based carbon nanotubes arranged in a repeating letter H-shaped fractal pattern. were.

They also made chips with nanotubes arranged in parallel lines, a design that one can see on a commercially available electrode chip.

Then, they tracked how mouse retinal neurons grew on the chips using cells cultured in a Petri dish.

The experiment showed that neurons are more prevalently associated with textured fractal branches than by smooth gaps between units. And glia, important support cells for neurons, are tightly packed in soft pores. Fractal design was most effective in this ‘herding’ of neurons and glia.

“The really clever thing is that we’ve managed to keep the glial cells in the gap,” Taylor said. “Glia are the life support system of neurons, and we need them to induce favorable interactions with both neurons and glial cells.”

The work is still in its early stages, Taylor emphasized. Ongoing trials in animals will include additional engineering and safety tests. But eventually, the researchers hope that their design will turn into a real-world device that can help people with vision loss.

And fractal-patterned, bio-inspired electrodes could be used in brain implant research beyond the bionic eye.

“I think it could help not only in the system we tested, but also implants in other parts of the nervous system,” Mosley said. “I hope that more researchers are moving towards using fractal electrodes instead of commercial patterns.”

Source: University of Oregon

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