Bioelectronics is the application of the principles of electronics to biology, being described as the research and development of bio-inspired electronic architectures down to the atomic scale in inorganic, and organic materials.  Therefore giving natural biological structures electrical properties without the use of electrical components is seen as the next step in bioelectronics and is highly desirable.  Now, a study from researchers at Rice University uses synthetic biology to develop artificial electrical switches built from a protein to control the flow of electrons into a cell.  The team states the proteins could facilitate next-generation bioelectronics, including complete biological circuits within cells capable of mimicking their electronic counterparts. The study is published in the journal Nature Chemical Biology.

Previous studies show natural proteins with the ability to move electrons are seen to act as permanent wires.  Nature typically controls electron flow by using genetic mechanisms to control the production of these protein-based wires.  Using transcriptional genetics, even in a fast-growing E. coli bacteria, it takes many minutes to produce and control these ‘wires’, in contrast, protein switches function on a time scale of seconds.  The current study develops ferredoxin logic gates in E. coli bacteria to control energy flow through a synthetic electron transfer pathway required for bacterial growth.

The current study uses ferredoxin, a common iron-sulfur protein mediating electron transfer, as the foundation for the switch embedded in a synthetic mutant strain of E. coli.  Results show the switch can be turned on in the presence, or off in the absence, of 4-hydroxytamoxifen, an estrogen receptor modulator, or bisphenol A, a synthetic chemical used in plastics.  Data findings show the ferredoxin switch acquires an electron cluster and can use different chemicals to control the production of a reduced metabolite in the E. coli. 

The lab explains their E. coli bacterium is a mutant strain programmed to only grow in a sulfate medium when all of the components of the ferredoxin electron transport chain, including electron donor and acceptor proteins, are expressed.  They go on to add it is in this way the bacteria can only grow if the switches turn on and transfer electrons as planned.  They conclude the possible applications for their technology includes living sensors, electronically controlled metabolic pathways for chemical synthesis and active pills able to sense their environment and release drugs on demand. 

The team surmises they have developed synthetic protein switches triggered by chemicals able to ‘electrify’ a living cell.  For the future, the researchers state their data should lead to custom-designed switches for many applications, including contact with external electronic devices.

Source: Rice University

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