"Living Robot" Life Forms Created from Frog Embryo Cells

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Friday, December 4, 2020
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Scientists in the United States claim to have created the world’s first living robots using stem cells from frog embryos. The tiny hybrids, designed on a supercomputer at the University of Vermont (UVM) and then assembled by biologists at Tufts University, are “entirely new life-forms” known as xenobots. “These are novel living machines,” said Joshua Bongard, a computer scientist and robotics expert at the UVM who co-led the research. “They’re neither a traditional robot nor a known species of animal. It’s a new class of artefact: a living, programmable organism.”

 

Frog 

 

According to the team, these millimetre-wide xenobots can move about and can also heal themselves after being cut. It is hoped the bots could one day be used to swim around human bodies to specific areas requiring medicine or to gather microplastic in the oceans. “We can imagine many useful applications of these living robots that other machines can’t do,” agreed Michael Levin, who directs the Center for Regenerative and Developmental Biology at Tufts, “like searching out nasty compounds or radioactive contamination, gathering microplastic in the oceans, travelling in arteries to scrape out plaque.”

 

Anatomical Blueprint of Living Robots

On the left, the anatomical blueprint for a computer-designed organism, discovered on a UVM supercomputer. On the right, the living organism, built entirely from frog skin (green) and heart muscle (red) cells. The background displays traces carved by a swarm of these new-to-nature organisms as they move through a field of particulate matter. (Credit: Sam Kriegman, UVM)

 

With months of processing time on UVM’s Deep Green supercomputer cluster at the Vermont Advanced Computing Core, the team used an algorithm to create thousands of candidate designs for the new life-forms. Attempting to achieve a task assigned by the scientists – such as locomotion in one direction – the computer would, over and over, reassemble a few hundred simulated cells into myriad forms and body shapes.

 

Living Robots GIF

 

As the programmes ran – driven by basic rules about the biophysics of what single frog skin and cardiac cells can do – the more successful simulated organisms were kept and refined. And after a hundred independent runs of the algorithm, the most promising designs were selected for testing.

 

Quadruped

A manufactured quadruped organism, 650-750 microns in diameter—a bit smaller than a pinhead

(Credit: Douglas Blackiston, Tufts University.)

 

Then the team at Tufts, led by Levin and with key work by microsurgeon Douglas Blackiston, transferred the in-silico designs into life. Firstly they gathered stem cells, harvested from the embryos of African frogs, the species Xenopus laevis (shown below) – hence the name ‘xenobots’ – and these were separated into single cells and left to incubate. Then, using tiny forceps and an even tinier electrode, the cells were cut and joined under a microscope into a close approximation of the designs specified by the supercomputer.

 

 

Following this, the team said the cells began to work together and “assembled into body forms never seen in nature”. The skin cells formed a more passive architecture, while the once-random contractions of heart muscle cells were put to work creating ordered forward motion as guided by the computer’s design, and aided by spontaneous self-organising patterns – allowing the robots to move on their own. The researchers found that the reconfigurable organisms were able to move in a coherent fashion and explore their watery environment for days or weeks, powered by embryonic energy stores. However, they later found they failed, describing them as beetles who “flipped on their backs”. Later tests showed that groups of xenobots would move around in circles, pushing pellets into a central location, spontaneously and collectively. Others were built with a hole through the centre to reduce drag.

 

joshbongard U of Vermont

 

In simulated versions of these, the scientists were able to repurpose this hole as a pouch to successfully carry an object. “It’s a step toward using computer-designed organisms for intelligent drug delivery,” said Bongard. “You look at the cells we’ve been building on xenobots with, and, genomically, they’re frogs,” said Levin. “It’s 100 per cent frog DNA – but these are not frogs.” He added: “As we’ve shown, these frog cells can be coaxed to make interesting living forms that are completely different from what their default anatomy would be.” The results of the new research were published in the Proceedings of the National Academy of Sciences.