Living robots made in the lab have found a new way to self-replicate, researchers say

Scientists say they have witnessed a type of replication never seen before in organic robots created in the laboratory using frog cells. Among other things, the findings could have implications for regenerative medicine.

The discovery involves a xenobot – a simple, “programmable” organism that is created by assembling stem cells in a Petri dish – and is described by a team of researchers from Tufts University, Harvard University and the University of Vermont in an article published this week. in the Proceedings of the National Academy of Sciences.

“You can think of it as using the different cells [as] building blocks like you would with LEGO or Minecraft, ”Douglas Blackiston, co-author of the study, told NPR.

The researchers hope that one day these xenobots – described by the same team in an article published nearly two years ago – could be programmed to perform useful functions such as finding cancer cells in the human body or trapping cancer. harmful microplastics in the ocean.

Xenobots are made up of cells taken from the African clawed frog, or Xenopus laevis. The cells are not genetically modified at all, but simply combined in different arrangements to produce the xenobots, says Blackiston, senior scientist at the Allen Discovery Center at Tufts University and the Wyss Institute for Biologically Inspired Engineering at Harvard University.

Xenobots propel themselves using tiny hair-like structures called eyelashes. They tend to twist like a corkscrew, which “turns out to be good enough to pick up a lot of things,” like other cells, Blackiston says.

So the team used an artificial intelligence-based computer simulation to see how they could manipulate the xenobots into shapes that would be even better for stacking things up.

Improved design yielded unexpected discovery

To that end, the initial spheroidal shape of the xenobots is “not the best design,” Blackiston explains. Instead, the computer suggested a C-shape similar to a snowplow or, as some have observed, Pac-Man. This form, he says, is very effective in gathering and collecting loose stem cells., which then form naturally in large piles.

But when the xenobots Scanned loose frog stem cells into the dish, the researchers observed something remarkable: The cell stacks were making copies of the original xenobots.

Various forms of sexual and asexual reproduction are of course well known in biology.

But what the xenobots did – dubbed kinematic self-replication – is new to living organisms, says Michael Levin, professor of biology at Tufts and an associate faculty member at the Wyss Institute. It happens at the molecular level, but “we don’t know of any organism that reproduces or replicates in this way,” he says.

It takes about five days to produce a copy under optimal conditions, according to the researchers. The “offspring” do not take on the C-shaped body type of the parental generation, but revert to the original, less efficient spheroid form.

Xenobots are collections of living cells and have no brain or digestive system. But in a real sense, they can be programmed – to circle other cells, like in this study, or possibly to do other things. This is why researchers consider them to be tiny organic robots.

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“The distinction between a robot and an organism is not as sharp as… we previously thought,” Levin told NPR. “These creatures, they have the properties of both.”

In fact, the idea of ​​kinematic self-replication isn’t entirely new – it was first suggested in the late 1940s by mathematician John von Neumann. He envisioned machines that could choose from basic robot parts to produce copies of themselves, says Sam Kreigman, postdoctoral researcher at the Wyss Institute and lead author of the article.

“Many people have been trying to make von Neumann machines from robot parts for a long time, and the success is limited,” Kreigman says.

“We found that if you let go of the assumption that the robot should be made of metal, circuit boards, and electronics, and instead use living cells, von Neumann machines are actually quite easy to make.” , he told NPR.

Some scientists have ethical concerns

But this worries some scientists. Nita Farahany, professor of law and philosophy at Duke University, studies the ethics involved in new technologies and was not part of xenobot research. “Whenever we try to exploit life … [we should] recognize its potential to go very badly, ”she told Smithsonian Magazine.

However, the researchers note that, like a hypothetical von Neumann machine, a xenobot cannot copy itself without raw materials. As a result, there is virtually no chance that they can escape the lab and start reproducing on their own. All the researchers have to do is remove the inventory of free stem cells, and there is nothing left to make new xenobots.

And since there is no genetic material from the parent xenobot, they also cannot mutate or evolve on their own, Blackiston explains.

“It would be like finding loose parts of a human that float and gluing them together to make a copy,” he says. “So it is difficult to understand how [evolutionary] selection would act on that, because there is nothing transferred between each generation – each is independent. ”

What the researchers hope is that one day these xenobots and their ability to self-replicate could be exploited for the good of humanity.

“It’s really a first step, but you can think about it all along,” says Blackiston. “If we could program them better, maybe they could select and selectively move the specific cell types that we want or help us shape something that we build into a dish for regenerative medicine. ”

What is interesting for Kreigman is that “this form of replication occurs spontaneously”. Of course, this requires very specific conditions, he says, but “it hasn’t had to evolve over billions of years”,

“We think about the time it took for life to evolve on Earth,” Kreigman says. “It’s a very long story, but here in a dish under the right conditions we have found a whole new form of replication in organisms.”

And discovering a new form of self-replication, he says, shows that “perhaps life is more expected than unexpected.”

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