Biorobots produce their own children –

They are called “xenobots” – the developers have now discovered another amazing ability of these biorobots grown from frog stem cells: engineered creatures can reproduce by aggregating free cells in suspension through their movements. In this way, the children of the Xenobots are born, which in turn can create new generations themselves. The experiments show that the efficiency of the first generation can be increased thanks to the C-shaped design. Scientists emphasize that the so-called kinematic self-replication is a previously unknown method of reproduction in living beings.

Man-made little creatures that can be sent on missions in complex environments: This futuristic concept has taken shape in the past few years. Scientists have already built partially microscopic robots with drives and certain capabilities. However, the building material was mainly metal or plastic, and the magnetic fields, for example, ensured movement. But over the past two years, a new concept has found its way into microrobotics: an American research team has presented millimeter-sized robots that are made of living cell tissue instead of artificial components. In this concept, the building material is Xenopus laevis stem cells. Based on this background, scientists call their designers xenobots.

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No genetic engineering is required for production – the process is based on the natural development potential of stem cells: scientists take this tissue from frog embryos and divide it into small units under a microscope. They are then grown in a nutrient medium. This, in turn, leads to the amazing growth of small clumps: they form into little spheres of about 3,000 cells, some of which are specialized. This creates a flagellar lash structure on the surface that moves in a targeted manner. In frogs, such so-called cilia are usually found on the mucous membranes and ensure the transport of foreign bodies. On the other hand, on the surface of spherical xenobots, they can provide the movement of a small cluster of cells.

In this way, biorobots can gather information from their surroundings or “sweep” particles in suspension. The latter effect now forms the basis of a new discovery: when scientists allowed some xenorobots to swim in liquid with free stem cells, they found that the tiny creatures pushed biological building material into small piles. Most importantly: over the course of five days, these lumps also formed xenobots that could move around. So the starting group took care of the development of the offspring.

The “Pac-Man” form increases reproductive capacity

Experiments have shown that some of the “children” were then able to support even the next generation. However, they were no longer as effective as their ‘parents’, since they are made up of fewer cells: the reproductive capacity of the next generation smaller drops significantly. “It’s hard to get the system to replicate further. That’s why they usually expire pretty quickly, ”says lead author Sam Kriegman of Tufts University in Medford. So, the researchers’ next step was to find out if it was possible to improve reproductive capacity by shaping the parental generation in a certain way. A computer system based on artificial intelligence was used for this purpose. It was found that a C-shape would be best for clumping cells. In this way, under the microscope, scientists have created a parental generation of xenobots that look like “Pac-Man” from the famous video game of the 1980s.

Experiments then confirmed that these versions were indeed able to collect a particularly large amount of cellular material. Then they created sufficiently large baby xenobots with increased ability to further reproduce. With shape-optimized parents, scientists finally lived to see four generations. In other words, Pac-Man’s xenobots had children, grandchildren, great-grandchildren, and ultimately great-great-grandchildren. However, they do not transmit their C shape: the offspring are spherical in shape, so they eventually become too small to produce the next generation.

Previously unknown to living things

The researchers explain that this phenomenon involves a form of propagation called kinematic self-replication. It is only known at the molecular level but has never been observed in organisms. “In our case, we have frog cells that replicate in a very different way than what, say, mature frogs do: no animal or plant known to science replicates that way,” says Kriegman.

According to the researchers, apart from possible applications of the system in bio-robots, the observations also reveal other interesting clues: “The fact that this unique replication strategy arises spontaneously and does not develop through specific selection is an example of plasticity in biological systems. Although kinematic self-replication has not been observed in modern cellular life forms, it may have been essential to the emergence of life, ‘the researchers write.

Source: University of Vermont, Journal Article: PNAS, doi: 10.1073 / pnas.2112672118

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