By Heiloi Yip
When asked to envision the future of biotechnology, one might think of a couple common images. Some may think about synthetic organisms using tissue pieced together from different species to form a ‘Frankenstein’s monster’. Others may think about a swarm of tiny robots that work together like ants might do, performing a variety of tasks as a collective whole. Recently, researchers have come up with something that combines these two ideas together.
Xenobots are spherical synthetic organisms composed of frog embryo cells. The name is derived from the species of frogs from where the cells were taken (Xenopus laevis), but they aren’t called ‘bots’ solely because they are an artificial creation. By definition, a robot is an automaton that completes any desired tasks, and that is exactly what researchers hope to accomplish with the xenobots. Each individual xenobot is very tiny, spanning less than 1mm in diameter. Depending on the structure of the xenobot, it may be capable of moving itself in a particular direction and interacting with any objects in the way. Although a single xenobot may appear to be a simple blob of cells, they reach their full potential when they can work together with other xenobots. Similar to how individual cells form organs in our body, each individual part acts together to carry out a much larger tasks. This principle of simple units assembling into an ‘intelligent’ collective is called emergent behaviour and forms the main principle behind the potential applications of xenobots (Ball, 2020).
The process to making a xenobot appears simple on the surface. Xenobots are currently composed of two kinds of embryonic cells: the epithelial progenitor cells (which forms the skin) and the cardiac progenitor cells (which forms the heart tissues). The skin cells act as scaffolding to provide structure for the xenobot’s body, while the heart cells’ ability to contract functions as the motor of the xenobot. The cells are extracted from frog embryos and then put together, to which the cells will begin adhering to each other by themselves. However, it is not as simple as randomly stitching cells together, as the arrangement of the various cells is very important to the behaviour of a single xenobot (and consequently a whole swarm of them). For this, computer algorithms are used to find an optimal arrangement of cells for any particular tasks. The algorithm achieves this by simulating evolution: it begins with a basic design, and then the algorithm generates multiple iterations of said design with a tiny tweak in each version. All designs are then subjected to a computer simulation to complete a task, with the best design being selected for the next generation of selection. Over time, the computer algorithm will find an optimal arrangement of cells for whatever task the algorithm was set to test for (Levin, 2020).
By and large, the potential applications of xenobots are wide ranging and very promising. One immediate field that might come into mind is in areas of medicine, where xenobots may be synthesized from the cells of the patients to avoid being targeted by the immune system. Their small size allows them to be injected into the patient’s body to perform a variety of vital tasks, such as removal of a blockage in the artery, or a tissue-specific administration of drugs. Xenobots are far from being limited to pharmaceutical applications, as they may serve industrial or environmental purposes. For example, xenobots could be released into the oceans programmed to sequester microplastics particles, allowing for a far easier method of cleaning up plastic pollution in the ocean. Since xenobots are composed of organic tissue (at least for now), they will biodegrade once they reach the end of their lifespan (currently 14 days but could possibly be lengthened in the future). Future iterations of xenobots could probably be synthesised using different cell types, perhaps even incorporating cell lines from different species, to allow an even wider range in functionality. More advanced computers may also pave way for increasingly complex simulations, producing more robust designs in the process (Kriegman et al., 2020).
Currently, xenobots are manually assembled cell-by-cell in a very labour intensive process. Mass production will definitely require some kind of unmanned automation if we are to acquire a complete swarm of xenobots. The future of xenobots also brings about multiple ethical considerations concerning the creation of new life. If a xenobot gains the ability to independently self-replicate, what if we can’t control the population of said xenobot? If a xenobot gets synthesised with neural tissue, what if it ends up creating an artificial sapience who deserves its own rights? As more and more research is being conducted on expanding the potential of xenobots, many of these difficult questions will inevitably need to be answered (Levin, Bongard & Lunshof, 2020).
References:
Ball, P. (2020). Living robots. Nature Materials. 19 (3), 265-265. Available from: doi:10.1038/s41563-020-0627-6
Kriegman, S., Blackiston, D., Levin, M. & Bongard, J. (2020). A scalable pipeline for designing reconfigurable organisms. Proceedings of the National Academy of Sciences. 117 (4), 1853-1859. Available from: doi:10.1073/pnas.1910837117
Levin, M. (2020). Life, death, and self: Fundamental questions of primitive cognition viewed through the lens of body plasticity and synthetic organisms. Biochemical and Biophysical Research Communications. 6 (291). Available from: doi:10.1016/j.bbrc.2020.10.077
Levin, M., Bongard, J. & Lunshof, J. (2020). Applications and ethics of computer-designed organisms. Nature Reviews Molecular Cell Biology. 21 (11), 655-656. Available from: doi:10.1038/s41580-020-00284-z
Imperial Bioscience Review 