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VIDEO: Living Robots Made From Frog Cells Can Now Self-Replicate, Scientists Say

Tiny, biological robots herd cells for “self-replication” in a world first.

A team of scientists reports they have discovered a new form of biological reproduction and have applied it to create the world’s first self-replicating living robots.

The team previously built the world’s first living robots, called Xenobots, named after the African clawed frog Xenopus laevis whose cells were used to build them. Now, by giving the Xenobots a new shape, researchers have found they can replicate.

“With the right design — they will spontaneously self-replicate,” said Joshua Bongard, a computer scientist and robotics expert at the University of Vermont.

The original Xenobots were spheres made up of about 3,000 cells. “These can make children but then the system normally dies out after that,” said Sam Kriegman, a post-doctoral researcher at Tufts’ Allen Center and Harvard University’s Wyss Institute for Biologically Inspired Engineering.

Researchers used an artificial intelligence program working on the Deep Green supercomputer cluster at UVM’s Vermont Advanced Computing Core, and an evolutionary algorithm was able to test billions of body shapes.

They found that C-shaped Xenobots resembling Pac-Man can swim and gather hundreds of single cells together and assemble “baby” Xenobots in their “mouth.” In just days, these new Xenobots resemble their parents and can swim. Never observed before, these new copies then seek out cells to build copies of themselves, and so on for multiple generations.

On the left is the design discovered by the AI computational search method in a simulation that was used to design the living Xenobot. On the right is the deployed physical organism, built completely from biological tissue (frog skin (green) and heart muscle (red)). (Sam Kriegman)

“It’s very non-intuitive. It looks very simple, but it’s not something a human engineer would come up with. Why one tiny mouth? Why not five?” said Kriegman, lead author of the study published in the Proceedings of the National Academy of Sciences,

Co-author Michael Levin said the embryonic cells “have the genome of a frog, but freed from becoming tadpoles, they use their collective intelligence … to do something astounding.”

“These are frog cells replicating in a way that is very different from how frogs do it. No animal or plant known to science replicates in this way,” said Kriegman.

While similar replication has been recorded at the molecular level, it had never been seen before at the scale of whole cells or organisms.

“People have thought for quite a long time that we’ve worked out all the ways that life can reproduce or replicate. But this is something that’s never been observed before,” said co-author Douglas Blackiston, the senior scientist at Tufts University who assembled the Xenobot “parents” and developed the biological portion of the new study.

Millimeter-sized Xenobots move in an aquatic environment, seeking out other cells for replication, leaving trails in their wake. (Douglas Blackiston)

Regarding concerns over negative consequences, Bongard said Xenobots “are not what keep me awake at night.”

Xenobots use energy from stored protein and fat and eventually degrade within a week, turning into dead skin cells. With each round of replication, smaller Xenobots are produced. When there are fewer than 50 cells, they lose the ability to swim and replicate.

They may even help with future pandemics, pollution and climate change. Bongard said scientists can now study how self-replicating systems work and how they can be controlled.

A Xenobot may also pick up and carry objects, such as microplastics dispersed in the ocean. By assembling the floating detritus into a mass, the microplastics can be more easily removed.

Researchers also say Xenobots may lead to medical advances. “If we can develop technologies, learning from Xenobots, where we can quickly tell the AI, ‘We need a biological tool that does X and Y and suppresses Z,’ that could be very beneficial. Today, that takes an exceedingly long time,” said Bongard.

Regenerative medicine is an area that could benefit. “If we knew how to tell collections of cells to do what we wanted them to do,” said Levin, “that’s the solution to traumatic injury, birth defects, cancer and aging.”

“All of these different problems are here because we don’t know how to predict and control what groups of cells are going to build. Xenobots are a new platform for teaching us,” said Levin.

Edited by Siân Speakman and Kristen Butler

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