Scientists have engineered what they say are the first self-replicating ‘robots’ ever made from living cells. Xenobots or “living robots” created from stem cells began to create new ones in a petri dish.
The unique features of the new robots will allow them in the future to cleanse the oceans of microplastics, detect and eliminate toxic materials, deliver drugs to the body or clean the arteries, scientists say.
In a recent study of organisms, scientists found that “living robots,” or xenobots, can reproduce. Named after the frog Xenopus laevis (smooth clawed frog), these xenobots are synthetic life forms invented in 2020, Science Alert writes.
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The breeding method of these xenobots is natural, since they are not a traditional robot made of metal, but contain organisms that can thrive on their own.
“For a long time, we believed that we knew all the ways organisms reproduce. However, this is something different, something that we have never seen before,” said study co-author Douglas Blackiston of Tufts University.
In their new study, scientists have given xenobots the ability to replicate themselves and create new versions of themselves. However, in this case, self-reproduction was not achieved using the methods of reproduction that we usually see in biological life forms.
To create self-replicating robots, the researchers removed stem cells from the skin and heart muscle of a smooth clawed frog embryo and incubated them in saline, after which some of the cells fused into a spheroid organism, on the outer layer of which flagella grew, allowing it to move.
The researchers found that if enough xenobots were placed in a Petri dish in close proximity to each other, then their collective movement would begin to accumulate other free frog cells floating nearby in the solution.
Once enough of these cells are brought together, a combined handful of about 50 cells will become a kind of xenobot offspring, capable of swimming on its own and amassing offspring of its own.
This phenomenon, called spontaneous kinematic self-reproduction, has already been observed in other kinds of molecular machines and models but never before in living multicellular systems like xenobots. Remarkably, this form of reproduction occurs spontaneously over several days, rather than developing over millennia.
When a handful of first-generation organisms were dipped into a second cup along with individual stem cells, the organisms’ movement gathered stem cells into handfuls, forming a new generation of organisms, which then repeated this behavior.
It is important to note that the same separated stem cells, left alone in solution, could not self-assemble. This indicates that for their formation into multicellular organisms, the initial movement of the xenobots-progenitors is necessary.
In addition, the team found that they can amplify this phenomenon by using artificial intelligence to simulate conditions that can improve self-replicating behavior.
“Simulations indicated that some body shapes amplified pile size and replication rounds, while others damped or halted self-replication,” the researchers explain. “Some but not all geometries were better than the spheroids.”
Ultimately, the Pac-Man-like C shape was the best candidate for combining free frog cells into new organisms. Also, scientists were helped by environmental modifications – the creation of walls that limited the movement of xenobots.
“Despite the fact that we are just starting to work with these ‘living robots’, one day they will be able to do useful work for us if we continue to figure out how they function, as well as learn how to control them. will be used in medical applications, as well as for collecting microplastics,” the scientists concluded.
At first, these freaky-looking ‘xenobots’ might seem notable for their superficial resemblance to Pac-Man, but their likeness to the video game character is probably the least strange thing about them.
These unusual robotic creatures are a spin-off of what the same researchers unveiled last year, when they presented the world’s first robots constructed entirely out of living cells – in this case, stem cells taken from embryonic frogs.
“These are novel living machines,” computer scientist and roboticist Joshua Bongard from the University of Vermont explained at the time.
“They’re neither a traditional robot nor a known species of animal. It’s a new class of artifact: a living, programmable organism.”
Now, Bongard and his collaborators have taken the next step, giving the xenobots the ability to self-replicate and spawn new versions of themselves.
In this case, the self-replication isn’t achieved by the kind of reproduction techniques we ordinarily see in biological life-forms.
Instead, the researchers found that if they put enough of the xenobots in close proximity with one another in a petri dish, their collective movement began to pile up other loose frog cells floating alongside in the solution.
Once enough of those cells were stacked together, the aggregated heap of about 50 cells became a kind of offspring to the xenobot organism, capable of swimming by itself, and in so doing, piling up its own offspring.
The phenomenon, called spontaneous kinematic self-replication, has been seen before in other kinds of molecular machines and models, but never before in living multicellular systems like the xenobots.
“We find that synthetic multicellular assemblies can also replicate kinematically by moving and compressing dissociated cells in their environment into functional self-copies,” the researchers explain in a new paper describing the reconfigurable organisms.
“This form of perpetuation, previously unseen in any organism, arises spontaneously over days rather than evolving over millennia.”
(Sam Kriegman and Douglas Blackiston)
Above: Simulation (left) predicts actual self-replication system in vitro (right).
To make the self-replicating robots, the researchers extracted pluripotent stem cells from African clawed frog (Xenopus laevis) embryo skins and incubated them in a saline solution, during which time a number of the cells would adhere into a spheroid organism, growing cilia on its outer layer which enabled it to move around.
When a dozen of the first-generation organisms were dropped into a second dish along with dissociated stem cells, the movement of the organisms clumped the stem cells into piles that formed a new generation of organisms, which then proceeded to repeat the same behavior of stacking up cells into heaps.
However, the same dissociated stem cells left alone in solution did not self-assemble, showing they needed the initial movement of the progenitor xenobots to trigger their formation into aggregated organisms.
That this kinematic self-replication, a behavior never before seen in plants or animals, could arise without genetic modification, demonstrates how radically biological entities can adapt and change in response to their environment, the researchers explained in their paper.
The team also found they could amplify the phenomenon by using artificial intelligence to simulate conditions that might enhance the self-replicating behaviors.
Ultimately the semitorus shape (Pac-Man in 3D, basically) was the best candidate for piling loose frog cells into new organisms, and modifications to the environment – introducing walls that constrain the movement of the xenobots – also helped.
While we’re still very much at the beginning of tampering with these living robot creatures, the researchers say the unusual organisms could one day perform useful work, if we can keep figuring out how they function, and also decide the right jobs to give them.
“This suggests that future technologies may, with little outside guidance, become more useful as they spread,” the team explains, “and that life harbors surprising behaviors just below the surface, waiting to be uncovered.”
The findings are reported in PNAS.
A year ago, American scientists created living, programmable organisms, The Guardian reported.
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Meanwhile, 193 countries adopted the first global agreement on the Ethics of Artificial Intelligence. You may read more here.
