Evolutionary biologists at Tufts University in Massachusetts have created so-called “neuro-robots” – small cell clusters capable of swimming in water, composed of a combination of embryonic cells and frog neural tissue. The findings of this research have been published in the journal Advanced Science.
This investigation builds upon prior work by the group led by Michael Levin, which first reported the creation of “biological robots” from the cells of the African clawed frog, Xenopus laevis, back in 2020.
These earlier developments were capable of performing several tricks, including crawling across surfaces and self-replication by moving free-floating cells to form new bio-robots, repeating this process for up to four generations. Researchers have now incorporated neural cells into this system to explore the novel behavioral capabilities they might enable.
“This all touches on very fundamental questions, namely: can a nervous system at all develop in a completely novel context that isn’t the product of millions of years of natural selection, and if so, how does it engage with and function in that artificial biological environment, or even how does it modify and enhance its reactions and behaviors,” Levin stated.
To construct the neuro-robots, researchers utilized developing skin tissue from frog embryos and introduced precursor nerve cells from another set of embryos. Shortly thereafter, the skin cells formed a spherical shape around the neural cells.
The result was a structure with a cell type on its surface known as a multiciliated cell (MCC). These cells naturally occur on the surface of Xenopus embryos and are covered in delicate protein “hairs” that sway, propelling the neuro-robot forward.
“The integration of the nervous system changes the morphology and function of the neuro-robots,” said co-author Haleh Fotovat. “Compared to the bio-robots, the neuro-robots are more elongated, display distinct MCC expression patterns, exhibit increased activity and more complex spontaneous behaviors, and undergo substantial shifts in global gene expression.”
The researchers also observed that the neuro-robots engaged in more complex movements compared to standard bio-robots, and that the complexity of these movements increased when they were treated with a drug that stimulates neural activity.
Levin views neuro-robots, and bio-robots in general, as a novel paradigm of life, potentially demonstrating how, despite possessing the same genetic code as a frog, the same cells can exhibit entirely different behaviors in new circumstances.
He also hopes they will find applications in medicine in the future; indeed, a previous experiment by the group showed that the presence of bio-robots created from human cells could enhance the speed of nerve cell regeneration across a scratch-induced injury.
However, others have been somewhat less enthusiastic in their praise in the past, particularly regarding whether cell clusters moving in this manner can truly be considered “robots.”
For some, the fact that structures derived from frog embryos are capable of this is not particularly surprising. Embryologist Jamie Davies from the University of Edinburgh in Scotland summarized: “Overall, the Xenopus embryo research community, familiar with these cells, didn’t quite understand what the big deal was.”
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