Xenobots are made from frog heart and skin cells
A research and development team from Tufts University (USA) and the University of Vermont (UVM) has successfully developed a second generation of miniature bio-robots called Xenobots, also based on African Xenopus cells, according to Tech Xplore. “The second generation of Xenobots is also based on African Xenopus cells.
Compared with the first generation, the second generation Xenobots can not only combine single cells autonomously, but also move faster, read and write information, and have a much better self-healing ability.
This latest research was published in the journal Science Robotics on March 31, 2011. (synthetic living machines); link to the paper: https://robotics.sciencemag.org/content/6/52/eabf1571″.
Back in January last year, the team released Xenobots, the world’s first living robot, which was featured on the cover of the top journal Proceedings of the National Academy of Sciences (PNAS). The research proposed and realized the concept of designing living organisms by computer and using biological materials instead of artificial materials such as metals and plastics to build robots.
I. Building organisms by frog embryonic stem cell differentiation
In terms of cellular construction, the first generation of Xenobots used a “top-down” construction method, in which the frog skin and heart cells were reconstituted by hand, and the heart cells contracted at the bottom layer to realize the robot’s movement.
In contrast, the second-generation Xenobots were constructed using a “bottom-up” approach, with individual cells forming the organism autonomously. Tufts University biologists used embryonic stem cells from an African frog, the Xenopus laevis (which gives Xenobots their name), to grow and proliferate, and within a few days some of the stem cells had differentiated to form cilia. These mobile, rotating cilia act as the “legs” of the second-generation Xenobots, allowing them to move quickly without muscle cells.
Thanks to the upgraded construction, the second-generation Xenobots can move faster, live longer, and adapt better to various environments.
The computer generates the design on the left side, which was used to develop the living robot on the right side
“We witnessed the extraordinary plasticity of cellular tissues – they defied common sense and built a new frog ‘body’ and this one with a completely normal genome.” said Michael Levin, a distinguished professor of biology at Tufts University. “In a normal frog embryo, cells proliferate and differentiate to form tadpoles. And now we see that the cells can redifferentiate to form cilia for motor function. Surprisingly, the cells can spontaneously assume new roles and create new bodies and behaviors without the need for long periods of evolutionary selection.”
“In a way, second-generation Xenobots resemble the construction of traditional robots; we’re just replacing artificial components with cells and tissues to build shapes and create predictable behaviors.” Senior scientist Doug Blackiston said. “In biology, this approach better explains how cells interact during development and how we can better control those interactions.”
Second, new Xenobots may be used to collect particles
The team, led by computer scientist and robotics expert Josh Bongard, ran evolutionary algorithms through a cluster of Deep Green supercomputers with advanced computing cores under hundreds of thousands of random environmental conditions to test whether Xenobots of different shapes, individually or in groups, would behave differently and to discern which groups of Xenobots would be best suited to working together in a particle field that collects a large number of fragments.
Algorithms can generate many different combinations of frog cells
The results show that second-generation Xenobots perform better in tasks such as garbage collection compared to first-generation Xenobots. On the one hand, second-generation Xenobots can sweep through petri dishes in swarms and collect large piles of iron oxide particles; on the other hand, they can work both on large flat surfaces and through narrow capillaries.
Not only that, but their research suggests that future silicon simulations could optimize additional functions of the bio-robots to generate more complex behaviors.
“Although the tasks of the current second-generation Xenobots are all simple, our ultimate goal is to develop a new type of living tool that will allow them to do more practical and useful work, such as cleaning up microplastics or soil contaminants in the ocean.” Bongard said.
Third, building read-write capabilities through fluorescent reporter proteins
One of the greatest features of robotics is the ability to record information and control the robot’s behavior based on that information.
In this regard, the research team recorded information through a fluorescent reporter protein called EosFP, which normally emits green light but emits red light when illuminated by light at a wavelength of 390 nm, as a way to design second-generation Xenobots as a robot with read-write capabilities.
Specifically, the researchers injected messenger RNA encoding the EosFP protein into frog embryonic cells and isolated stem cells to form second-generation Xenobots, which will have a built-in fluorescent switch that can record blue light exposure at around 390 nm.
In a real-world test, the researchers had 10 second-generation Xenobots swim on a surface while there was a spot on that surface that was illuminated by a beam of light at a wavelength of 390 nm. After two hours, three of the robots glowed red and the rest stayed green. This shows that the “journey memory” was effectively recorded.
Xenobots can live in fresh water for up to 7 days
The researchers believe that this principle of molecular memory may be used in the future to detect and record light pollution, radioactive pollution, chemical pollution, drugs or diseases. Also, the researchers gave different optimization paths for Xenobots’ recording system, such as having the robot record multiple stimuli (more bits of information need to be added) and release compounds in response to stimuli, or change behavior depending on the sensation of different stimuli.
“While we give the robots more capabilities, we can use computer simulations to design more complex behaviors and allow them to perform more complex tasks.” Bongard spoke of their design of robots that can not only report the condition of the environment they are in, but also modify and repair the condition of the environment they are in.
Fourth, biomaterials have a strong healing metabolism and self-heal severe lacerations in five minutes
“We hope to apply many of the properties of biomaterials to robots, such as using cells to form sensors, motors, communication and computing networks, and information storage devices.” Levin said.
In Levin’s view, healing is a natural characteristic of living organisms and is difficult to do with traditional metal or plastic robots. But second-generation Xenobots and future bio-robots can build their own bodies as cells grow and mature, and repair themselves when damaged.
The second-generation Xenobots are known to be so good at healing that they can heal severe lacerations in five minutes, with wounds nearly half the thickness of their bodies. In real-world tests, all injured robots recovered as before and were able to continue working.
Xenobots 2.0
Not only that, but the second generation of Xenobots can also perform metabolism. Unlike metal or plastic robots, the cells of second-generation Xenobots can absorb and break down chemicals, and synthesize and expel chemicals and proteins like mini factories.
Meanwhile, synthetic biology, which previously focused on single-cell organisms, has been able to study these multicellular organisms or can reprogram them to produce useful molecules.
Similar to first-generation Xenobots, second-generation Xenobots can survive for 10 days on embryonic energy reserves and perform their tasks without additional energy. With a continuous supply of energy, they can operate at full speed for several months.
Conclusion: Biotechnology and robotics reciprocate with a promising future
The development of living robots continues to see breakthroughs in technology, and the future of this field will be inextricably linked to biotechnology.
As Michael Levin mentioned in his TED talk, second-generation Xenobots have extraordinary potential to perform tasks or medical treatments, and the value of this research lies in using robotic studies to understand how individual cells gather in, communicate, and create organisms. This is a new model system that might allow for some research in regenerative medicine based on this system.
Recognizing the promise of this technology, Tufts University and the University of Vermont have established the Institute for Computer Designed Organisms (ICDO), which will be officially launched in the coming months. The institute will bring together universities and external resources to create more advanced and capable bio-robots.
In future research, second-generation Xenobots and higher versions of living robots may be able to draw more inspiration from the field of biology.
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