PART-HUMAN, PART-MACHINE TRANSISTOR DEVISED

By embedding a nano-sized transistor inside a cell-like membrane, scientists link humans and machines more intimately than ever.                

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An artist’s representation of a new transistor that's contained within a cell-like membrane. In the core of the device is a silicon nanowire (grey), covered with a lipid bilayer (blue). Click to enlarge this image. 
Scott Dougherty, LLNL 

Man and machine can now be linked more intimately than ever, according to a new article in the journal ACS Nano Letters. Scientists have embedded a nano-sized transistor inside a cell-like membrane and powered it using the cell's own fuel.

The research could lead to new types of man-machine interactions where embedded devices could relay information about the inner workings of disease-related proteins inside the cell membrane, and eventually lead to new ways to read, and even influence, brain or nerve cells.

"This device is as close to the seamless marriage of biological and electronic structures as anything else that people did before," said Aleksandr Noy, a scientist at the University of California, Merced who is a co-author on the recent ACS Nano Letters. "We can take proteins, real biological machines, and make them part of a working microelectronic circuit."

To create the implanted circuit, the UC scientists began with a simple transistor, an electronic device that is the heart of nearly every cell phone and computer on the planet. Instead of using silicon, the most common material used in transistors, the scientists used a next generation material known as a carbon nanotube, a tiny straw-shaped material made from a single curved layer of carbon atoms arranged like the panels of a soccer ball.

The scientists then coated the carbon nanotube transistor with a lipid bilayer, basically a double wall of oil molecules that cells use to separate their insides from their environment. The scientists didn't use an actual cell membrane, however.

To this basic cellular structure the UC scientists added an ion pump, a biological device that pumps charged atoms of calcium, potassium, and other elements into and out of the cell. Then they added a solution of adenosine tri-phosphate, or ATP, which fuels the ion pump.

The ion pump changes the electrical charge inside the cell, which then changes the electrical charge going through the transistor, which the scientists could measure and monitor.

In their initial device the biological pump powered the artificial transistor. Future devices could work just the opposite, where an outside electrical current could power the pump and alter how quickly ions are pumped into or out of a cell. That could have dramatic effects.

For instance, instead of using drugs to block the release or uptake of various drugs or neurotransmitters, scientists could change the electricity regulating the ion pump, which would then change the amount of the drug or molecule inside, or outside, the cell.

Other groups have tried to mix man and machine before, said Itamar Willner, a scientist from the Hebrew University of Jerusalem, but none have achieved this level of intimacy.

"Previous students used enzymes that were not incorporated into membranes in the transistors," said Willner. "In this case, an enzyme that usually works in the membrane was linked to carbon nanotubes."

The new enzyme-transistor link could help eventually monitor and even treat diseases and conditions, said Willner.

Some of the most obvious medical conditions the embedded transistor could help study, or alleviate, are toxins and poisons. Many of these chemicals puncture cell membranes and cause the cell's inner fluid, or cytoplasm, to leak out, essentially bleeding the cell to death. Other toxins create ion imbalances inside the cells, which can cause paralysis and other conditions.

If the cells could be encouraged to pump the necessary ions into or out of the cell that could help treat a specific condition. Though any actual treatment based on this technology is still years away, said Willner.

"We don't want to just sense things, we also want to treat them," said Willner. Clinical applications may still be years away, but the new research is the most intimate link between life and machines that has yet been created.