Bio-robots produce their own babies

A “Pac-Man bio-robot” (red) collects loose stem cells in its environment and condenses them into a ball (green) that can develop into a new bio-robot. (Image: Douglas Blackiston)

They are called “xenobots” – the developers have now discovered another amazing ability in these bio-robots bred from frog stem cells: the designer beings can reproduce by moving free cells together in a suspension. This creates Xenobot children, who in turn can then produce new generations themselves. The experiments show that the effectiveness of the first generation can be increased with a C-shaped design. The researchers emphasize that what is known as kinematic self-replication is a mode of reproduction previously unknown to living beings.

Man-made tiny things that can be sent on missions in complex environments: this futuristic-looking concept has taken on more and more shape in recent years. Researchers have already constructed some microscopic robots with drives and specific capabilities. The building material, however, was mostly metal or plastic and magnetic fields, for example, ensured movement. But in the last two years a new concept has found its way into microrobotics: a US research team presented millimeter-sized robots that are made from living cell tissue instead of artificial components. In this concept, the building material consists of stem cells from the frog Xenopus laevis. Based on this origin, the scientists call their designer beings Xenobots.

Cilia make you mobile

Genetic engineering is not required for production – the process is based on the natural development potential of stem cells: The researchers take this tissue from frog embryos and break it down into small units under the microscope. They are then cultivated in nutrient medium. This then leads to an astonishing development of the small lumps: They independently form into small spheres of around 3000 cells, some of which specialize. This creates flagellate-like eyelashes on the surface of the structures, which move in a directional manner. In frogs, such so-called cilia are usually located on the mucous membranes and ensure that foreign bodies are transported away. On the other hand, on the surface of the spherical xenobots, they can ensure that the small cluster of cells moves.

In this way, the bio-robots can collect information from their environment or “sweep” particles together in a suspension. This second effect now forms the basis of the new discovery: When the researchers allowed some Xenobots to swim in a liquid with free stem cells, they found that the tiny things were pushing the biological building material together into small piles. The highlight: Within five days, Xenobots, which could move, also formed from these clumps. A start group had taken care of the development of the offspring.

A “Pac-Man” form increases reproductive capacity

Experiments have shown that some of the “children” were even able to look after another generation again afterwards. However, they were no longer as effective as their “parents” because they are made up of fewer cells: The reproductive capacity of the smaller subsequent generation is greatly reduced. “It’s hard to get the system to multiply. It therefore usually dies out very quickly, ”says lead author Sam Kriegman from Tufts University in Medford. Therefore, the researchers next sounded out whether the ability to reproduce could be improved by shaping the parents’ generation in a certain way. A computer system based on artificial intelligence was also used. It concluded that a C-shape would be best for pushing cells together into clumps. Under the microscope, the scientists created a parent generation of Xenobots that look like “Pac-Man” from the famous video game of the 1980s.

Experiments then confirmed that these versions were actually able to sweep together a particularly large amount of cell material. They then also formed correspondingly large child xenobots with an increased ability to further reproduce. With the form-optimized parents, the researchers finally achieved four generations. In other words, the Pac-Man Xenobots had children, grandchildren, great-grandchildren and, ultimately, great-great-grandchildren. However, they do not pass on their C-shape: The offspring have the spherical shape and so in the end they also become too small to produce another generation.

So far unknown by living beings

As the researchers explain, the phenomenon is a form of reproduction known as kinematic self-replication. So far it is only known at the molecular level, but it has never been observed in organisms. “In our case, we are dealing with frog cells that replicate in a way that is very different from how finished frogs do, for example: no animal or plant known to science replicates itself in this way.” says Kriegman.

According to the researchers, in addition to possible uses of the system in bio-robotics, the observations also provide other interesting indications: “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 yet been observed in today’s cellular life forms, it may have been essential in the origin of life, ”the researchers write.

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

Recent Articles

Related Stories

Stay on op - Ge the daily news in your inbox