'Living robot' life forms created from frog embryo cells

Scientists at the University of Vermont and Tufts University, Massachusetts have reported building so-called 'biological robots' for the first time. 

The study, published in Proceedings of the National Academy of Science (PNAS), reports generating the robots from frog embryos. 

'These are novel living machines,' Professor Joshua Bongard, engineering and robotics researcher at the University of Vermont and co-lead of the project, said. 'They're neither a traditional robot nor a known species of animal. It's a new class of artefact: a living, programmable organism.'

Termed 'xenobots', potential uses of these living robots are picking up microplastics in the ocean, finding and digesting toxic materials, removing plaque from arteries or delivering drugs to specific targets within the human body. The xenobots could also be used as a model system that facilitates research into areas such as genetics, development, regenerative biology and artificial life.  

A super-computer was used to generate thousands of evolutionary algorithms and the most promising of these were selected for production. Stem cells from embryos of African clawed frogs were used as building blocks and shaped to the desired anatomy using miniscule surgical tools and electrodes. The use of cardiac progenitor cells generated contractile waves that supported movement. 

Co-lead Michael Levin, professor of regenerative and developmental biology at Tufts University, Medford, Massachusetts described the novelty of the work, 'You look at the cells we've been building on xenobots with, and, genomically, they're frogs...but these are not frogs. As we've shown, these frog cells can be coaxed to make interesting living forms that are completely different from what their default anatomy would be.'

The xenobots produced were less than 1mm long, sometimes limb-like structures that could propel themselves forward, or holes to carry minute objects. A combination of passive and contractile cells from ectoderm, the outermost layer of an embryonic tissue, and cardiac cells respectively were structured in order to achieve the desired function. 

Advantages of the xenobots compared to traditional robots include their ability to self-repair, their naturally limited lifespan and the fact that they decompose. 'These xenobots are fully biodegradable,' said Professor Bongard. 'When they're done with their job after seven days, they're just dead skin cells.'

While at an early stage, the potential applications for this technology are broad. The xenobots were tested in their ability to perform tasks such as moving towards a target, working together and carrying or pushing pellets around. They might become especially useful as scientists find ways to train them to recognise receptors or other molecules of interest.