So-called "xenobots" could replace traditional metal or plastic robots without polluting the planet, but they raise several ethical questions.
These are xenobots, "living machines" with frog stem cells inside in a new configuration designed by a computer algorithm.
Photo by: (Kriegman et al., PNAS, 2020).
In the laboratory of Michael Levin at Tufts University, cells can expect to be in unusual company.
Living machines, the Frankensteins of the modern era
Here, frog skin precursors come close to cells that, in another life, might have helped an amphibian's heart beat. They are perfect strangers: biological entities that, up to this point, had no business relationships. Yet, Levin and his colleagues found that skin cells and heart cells can be pushed into coalescence. Placed side by side, they will self-organize into intricate three-dimensional mosaics of frog cells that are not frogs.
Engineered by a computer algorithm and surgically modeled by human hands, these living robots, heart-skin hybrids about the size of a grain of sand, resemble nothing found in nature.
But the tasks they perform are strangely familiar: Without any external input, they can move around Petri dishes, push microscopic objects back and forth, and even “adjust” themselves after being cut.
Levin defines (rightly, too) these groups of cells as "new forms of life": they are neither organisms nor machines, but perhaps something in between.
Called “xenobots” in honor of Xenopus laevis, the African frogs from which their cells are derived, have enormous potential to reveal the rules that govern how the building blocks of life are assembled.
With a lot of additional tweaks, xenobot technology could someday also be harnessed to deliver drugs around the body, harvest environmental contaminants, and more. Levin and his colleagues write it today in the magazine Proceedings of the National Academy of Sciences. Unlike traditional robots, the living, self-healing xenobots of the future could theoretically accomplish these feats without polluting the planet, and repair themselves in case of damage.
As plastics and other hard-to-degrade polymers continue to accumulate in the environment, “the incredibly innovative approach” offered by xenobots “It could be really important for sustainability”, he claims Tara Deans, biomedical engineer and synthetic biologist at the University of Utah.
But xenobots also raise a number of ethical questions
Maybe it sounds a little apocalyptic, but if things get bad humans may need protection from these and other artificial life forms. “When you create life, you don't have a good idea of what direction it will take,” says Nita Farahany, who studies the ethical implications of new technologies at Duke University. “Every time we try to exploit life,” she says, “we should recognize that it can end badly.”
Over the past few decades, humanity has made incredible advances in robotics. Machines can now master difficult board games and navigate difficult terrain; they can drive themselves as autonomous vehicles and search for survivors following disasters. But even in their most creative configurations, metals and plastics simply can't measure up to cells.
Biological systems: much more advanced than mechanical robots
“Biological systems are the envy of robotics”, he claims Levin. “They are adaptable, flexible, they repair themselves. There are no robots in the world that can actually do this.”
That's why Levin and his colleagues decided to make one. Together with robotics experts Sam Kriegman e Josh Bongard from the University of Vermont, asked a computer algorithm to design a series of living machines, using frog skin and heart cells as raw materials. The algorithm was trained to optimize each xenobot for a different basic function, such as moving back and forth or manipulating objects.
After testing different configurations, the algorithm selects the digital projects that it deems most suitable for the task at hand. The researchers then attempt to recreate these designs in Levin's lab.
Photo by: (Kriegman et al., PNAS, 2020)
“Cells like to be together”
Even after being scraped from frog embryos and smashed into a fluid-filled disc, the skin and heart cells will race to unite. “Cells love being together”says Levin. He's the microsurgeon who took the newborn living robots and sculpted them into the shapes specified by the computer.
All of the xenobots' ingredients come from an actual frog, but there's nothing amphibious about the final forms they've taken. Some have turned into disjointed shapes. others have taken the form of hollow prism-like structures. The robots lacked limbs, skeletons and nervous systems. But they easily coped with the tasks they were designed for.
Without mouths or digestive systems, they are fed exclusively by the pieces of embryonic yolk with which they were "whipped". That's why they die after about a week when that culture liquid dries up, Bongard says. But he and his colleagues think robots could one day be used to deliver drugs into human bodies or scrape plaque from arteries. Released into the environment, they could monitor toxins or sweep microplastics out of the oceans.
The team is already experimenting with different types of cells, for different types of functions. The xenobots also appear to be able to create new versions of themselves, putting individual cells together until they begin to merge, Levin says. They are also resistant: once broken, the robots simply repair their wounds and continue.
And now the inevitable problems and some ethical doubts
A lot of good could come from this technology, but it's also important to consider potential risks. It also states this Susan anderson, philosopher and machine ethicist at the University of Connecticut. In the wrong hands, the xenobots' power could easily be exploited as a biological weapon. It would carry poisons into people's bodies instead of medicines.
Humans already have tinkered with the recipes of life. In recent years, bioengineers have reprogrammed cells to churn out life-saving drugs, strip genomes to their lowest states, and hybridize animals with other animals (or with human cells).
But multicellular life forms synthesized from scratch are still few and far between. Also why much of biological development remains a mystery. Researchers are still not sure, for example, how tissues, organs and appendages manifest themselves.
Studying xenobots could certainly help crack that development code. But to get there, scientists will first have to experiment. Mastering techniques and technologies they don't fully understand. Starting from the machine learning algorithm that designs these life forms.
Bongard and his colleagues recognize the delicacy of their work. “the ethical problem surrounding this topic is not trivial”, says the scholar. Although the researchers have not yet brought bioethicists to see their research, “It's something we'll have to do. It's useful as part of the discussion about what to do with this technology."he adds. First, however, “We just wanted to show that this was possible.”
