Scientists at the University of Vermont and Tufts University used a supercomputer to evolve a design for tiny living robots made out of frog cells, then assembled them. The tiny new creatures did what they were supposed to do --make their way across a Petri dish. They also had some surprises for the researchers.
“These are novel living machines,” Joshua Bongard, a computer scientist and robotics expert at the University of Vermont who co-led the new research, said in a statement. “They’re neither a traditional robot nor a known species of animal. It’s a new class of artifact: a living, programmable organism.”
The research results were published Monday in the Proceedings of the National Academy of Sciences. The first author was UVM doctoral student Sam Kriegman.
The new “biobots” were designed on the Deep Green supercomputer cluster at UVM’s Vermont Advanced Computing Core. Bongard said that in 100 runs, the supercomputer considered billions of designs, looking for a design for a creature that would travel across the bottom of a Petri dish as quickly as possible.
“The design we built wasn’t imagined by a human. It was created by an AI,” he said in a telephone interview. “We used an evolutionary algorithm, a computer program which, in virtual words, evolves virtual creations."
The biobots were then actually assembled out of living cells at Tufts by a team led by study co-leader Michael Levin who directs the Center for Regenerative and Developmental Biology at Tufts, with key work by microsurgeon Douglas Blackiston.
The team gathered cells from the embryos of African frogs, the species Xenopus laevis. Then, using tiny forceps and an even tinier electrode, the cells were assembled under a microscope into a close approximation of the designs specified by the computer, the statement said.
The result was a creature between a half-millimeter and a millimeter in diameter, Levin said, that included frog skin cells and heart muscle cells.
The heart muscle cells in the creature then went to work, contracting and creating an “inchworming” motion that moved the creature along, Levin said. The biobots last for about seven days and then they “sort of degrade and rot away,” Bongard said.
To see the biobots in action, moving across the dish, Levin said in a telephone interview, was “unbelievable.”
But that was not all: The biobots repaired themselves when they were sliced almost in half, stitching themselves up and keeping going. And, when several were introduced into a Petri dish strewn with small pellets, the biobots engaged in a kind of herding motion.
“It turns out they sort of act like sheep dogs,” said Bongard.
Bongard said the biobots displayed “additional behavior above and beyond what we asked for," suggesting that, in the case of the self-repair, "The cells realize that the organism, although it’s a new shape, it’s still an organism and the cells need to repair the damage.” As for the herding, he said, researchers “have very little idea why this occurs.”
The study suggested that there were “numerous" possible applications for the biobots. “Given their nontoxicity and self-limiting lifespan, [the biobots] could serve as a novel vehicle for intelligent drug delivery or internal surgery," the study said. Researchers also suggested, among other things, that biobots could remove plaque from artery walls, identify cancer, or help in cleaning up microplastics in the ocean.
The research could also have massive implications for regenerative medicine, Levin said, casting more light on the mystery of how cells cooperate to build complex, functional bodies like human organs.
In the study, he said, “Normal frog cells are spontaneously able to get together and make a completely different kind of organism."
“The big thing we’re discovering is that the cells are trying to build coherent structures,” he said. “Even in this really weird, novel environment, the cells are working hard to make something functional. The cells want to do it.”
The future of regenerative medicine, he said, could be a kind of “guided self-assembly ... motivating cells to make specific structures, not micromanaging them.”
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