Stem cells are unspecialized cells that have the ability to develop into different cell types. To make the xenobots, the researchers scraped living stem cells from frog embryos and left them to incubate. There’s no manipulation of genes involved.
“Most people think of robots as made of metals and ceramics but it’s not so much what a robot is made from but what it does, which is act on its own on behalf of people,” said Josh Bongard, a computer science professor and robotics expert at the University of Vermont and lead author of the study.
“In that way it’s a robot but it’s also clearly an organism made from genetically unmodified frog cell.”
Bongard said they found that the xenobots, which were initially sphere-shaped and made from around 3,000 cells, could replicate. But it happened rarely and only in specific circumstances. The xenobots used “kinetic replication” — a process that is known to occur at the molecular level but has never been observed before at the scale of whole cells or organisms, Bongard said.
With the help of artificial intelligence, the researchers then tested billions of body shapes to make the xenobots more effective at this type of replication. The supercomputer came up with a C-shape that resembled Pac-Man, the 1980s video game. They found it was able to find tiny stem cells in a petri dish, gather hundreds of them inside its mouth, and a few days later the bundle of cells became new xenobots.
The parent rotates a large ball of stem cells that is maturing into a new xenobot.
“The AI didn’t program these machines in the way we usually think about writing code. It shaped and sculpted and came up with this Pac-Man shape,” Bongard said.
“The shape is, in essence, the program. The shape influences how the xenobots behave to amplify this incredibly surprising process.”
The xenobots are very early technology — think of a 1940s computer — and don’t yet have any practical applications. However, this combination of molecular biology and artificial intelligence could potentially be used in a host of tasks in the body and the environment, according to the researchers. This may include things like collecting microplastics in the oceans, inspecting root systems and regenerative medicine.
While the prospect of self-replicating biotechnology could spark concern, the researchers said that the living machines were entirely contained in a lab and easily extinguished, as they are biodegradable and regulated by ethics experts.
The research was partially funded by the Defense Advanced Research Projects Agency, a federal agency that oversees the development of technology for military use.
“There are many things that are possible if we take advantage of this kind of plasticity and ability of cells to solve problems,” Bongard said.
The
study was published in the peer-reviewed scientific journal PNAS on Monday.
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