Biological computer that 'lives' inside the body comes one step closer as scientists make transistor out of DNA and RNA

Finding could lead to new biodegradable devices based on living cells that are capable of detecting changes in the environment

Scientists believe they are close to building the first truly biological computer made from the organic molecules of life and capable of working within the living cells of organisms ranging from microbes to man.

The researchers said that they have made a transistor – the critical switch at the heart of all computers – from DNA and RNA, the two biological molecules that store the information necessary for living things to replicate and grow.

Silicon transistors control the direction of flow of electrical impulses within computer chips, but the biological transistor controls the movement of an enzyme called RNA polymerase along a strand of the DNA molecule, the scientists said.

Ultimately, the aim is to use the biological transistors – called transcriptors – to make simple but extremely small biological computers that could be programmed to monitor and perhaps affect the functioning of the living cells in which they operate, researchers said.

It could lead to new biodegradable devices based on living cells that are capable of detecting changes in the environment, or intelligent microscopic vehicles for delivering drugs within the body, or a biological monitor for counting number of times a human cell divides so that the device could destroy the cell if it became cancerous, the scientists said.

“Biological computers can be used to study and reprogram living systems, monitor environments and improve cellular therapeutics,” said Drew Endy, assistant professor of bioengineering at Stanford University in California, who led the study published in the journal Science.

Last year, Professor Endy announced new ways of using biological molecules to store information and to transmit data from one cell to another. The latest study adds the third critical component of computing – a biological transistor that acts as a “logic gate” to determine whether a biochemical question is true or false.

Logic gates are critical for a computer to function properly. In a biological setting the use of logical data processing is almost as limitless as its use in conventional electronic computing, said Jerome Bonnet, a bioengineer within the Endy laboratory, and the lead author of the study.

“You could test whether a given cell had been exposed to any number of external stimuli – the presence of glucose and caffeine for instance. [Logic] gates would allow you to make the determination and store that information so you could easily identify those which had been exposed and which had not,” Dr Bonnet said.

Biological computers have been the dream of electronic engineers for decades because they open the possibility of a new generation of ultra-small, ultra-fast devices that could be incorporated into the machinery of living organisms.

“For example, suppose we could partner with microbes and plants to record events, natural or otherwise, and convert this information into easily observed signals. That would greatly expand our ability to monitor the environment,” Professor Endy said.

“So the future of computing need not only be a question of putting people and things together with ubiquitous silicon computers. The future will be much richer if we can imagine new modes of computing in new places and with new materials – and then find ways to bring those new modes to life,” he said.