Not alive, not dead, but a third state. Sounds spooky, but it’s the future of medicine. More specifically, this ‘third state’ is when the cells of an organism adopt new functions even after ‘death’. Or in other words, the cells are functioning, but the being is dead. And this spooky phenomenon is revolutionising synthetic biology as, usually, death is considered to be irreversible. But with this new discovery of a ‘third state,’ different cells from a range of organisms can be repurposed into biological ‘robots’. But what can they do?
In a review published in the journal Physiology, researchers are contemplating the implications of taking cells from organisms (dead or alive) and turning them into biological robots that have new functions. For example, researchers have managed to successfully create tiny 'robots' from human cells which could be used to heal wounds, regenerate tissue and treat diseases, known as anthrobots. In another instance, researchers from Tufts University in Massachusetts have also created xenobots from the cells of already dead frogs. The cells, despite coming from a dead organism, can self replicate and perform simple tasks
The creation of these biobots essentially points to the ‘third state’. In The Conversation, biologists Dr Peter Noble and Dr Alex Pozhitkov, co-authors of the review, wrote: ‘The third state challenges how scientists typically understand cell behaviour. While caterpillars metamorphosing into butterflies, or tadpoles evolving into frogs, may be familiar developmental transformations, there are few instances where organisms change in ways that are not predetermined. Tumours, organoids and cell lines that can indefinitely divide in a petri dish, like HeLa cells, are not considered part of the third state because they do not develop new function’
So, to break it down even further, third state ‘beings’ are those that can undertake new functions after death. This means cancer cells are also excluded, since they don’t exhibit new functions either. Going back to the anthrobots, they were taken from human lung cells. But somehow they managed to repair damaged neuron cells placed in a nearby petri dish. They managed to move by using their own hair like projections, also known as cilia
Dr Noble and Dr Pozhitkov wrote: ‘Taken together, these findings demonstrate the inherent plasticity of cellular systems and challenge the idea that cells and organisms can evolve only in predetermined ways. Taken together, these findings demonstrate the inherent plasticity of cellular systems and challenge the idea that cells and organisms can evolve only in predetermined ways’
Although the third state beings have semi-cheated death, they only last for no more than 60 days, and biograde when they’re dead – they are natural organisms, after all. Even so, 60 days is still a wonder since it's unclear how these repurposed cells are able to live so long after an organism dies, and we still don’t know the extent of their new functions
The authors give one hypothesis, however: ‘One hypothesis is that specialised channels and pumps embedded in the outer membranes of cells serve as intricate electrical circuits. These channels and pumps generate electrical signals that allow cells to communicate with each other and execute specific functions such as growth and movement, shaping the structure of the organism they form’
