Two-cell computers that transfer metabolic information from one cell to the other could lead to synthetic therapeutic hormone systems. 

The field of synthetic biology exists at the interface between engineering and biology, where biological parts are connected to form systems with useful functions. Often this involves creating networks of genes that respond to a change in environment, behaving, for example, like a logic gate. However, it has been difficult to design such networks in mammalian cells, and until recently, most developments were limited solely to operate in individual cells.

Both sender and receiver cells respond to arginine allowing each cell to affect the other

Now a team led by Martin Fussenegger, at the Swiss Federal Institute of Technology Zurich, has designed the first two-way network of communicating mammalian cells. The network is made up of a sender cell and a receiver cell. The receiver cell contains a previously developed expression system, which produces a fluorescent protein in response to raised arginine levels in the surrounding medium. These levels are regulated by the sender cell, which is engineered to express arginase, an enzyme that removes arginine by converting it to the amino acid ornithine. So, by controlling the amount of arginine, the sender cell transmits metabolic information to the receiver cell, which is converted to a fluorescent output.

Explaining his reasons for developing the system, Fusseneger says: 'We really dream of having prosthetic circuits that could be implanted into humans. These could sense pathological levels of molecules and trigger a therapeutic response. Instead of having to take a pill every day this would be a one-time treatment, solving the problem once and for all.' 

James Collins, a professor of biomedical engineering and co-director of the Center for BioDynamics, Boston University, US, says that the system is a brilliant achievement. 'This novel development opens up a number of bioengineering possibilities,' he adds, 'including the design of artificial hormone systems.' 

Bailey Fallon

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