DNA is a great way to store information—just ask your cells. Its molecules are stable, and billions of base pairs coil neatly into a few microns in a cell nucleus. While it’s easy for a cell to read information from DNA, a cell can’t rewrite new data into its DNA sequence.
But now synthetic biologists at Stanford have managed to pull off that very trick. To do so, they had to abandon the genetic code of ATCG and get a DNA sequence to act like bits—pieces of binary information—in a computer. The memory system uses two enzymes that can cut out and reintegrate a sequence of DNA in a live cell. Crucially, the attachment sites are designed so that the DNA sequence can be flipped every time it is put back in. The sequence oriented one way would represent 1, and its inversion is 0.
Left: normal rat disc. Right: engineered disc.
What’s the News: Researchers at Cornell University have now bio-engineered synthetic spinal discs and implanted them in rats. The implants provide as much spinal cushioning as authentic discs do, and improve with age by growing new cells and binding to nearby vertebrae, according to the study recently published in the journal PNAS. The research could someday help people with chronic lower back and neck pain from conditions like degenerative disc disease.
The synthetic trachea, just before implantation
What’s the News: An African man’s new trachea is the world’s first synthetic organ to be transplanted. Made from a polymer scaffold coated with the patient’s own cells, the windpipe seems to be working out well, more than a month after the surgery.
The implants of the future will be powered by the energy sources already inside your body. Last week we saw scientists take a step toward this vision by developing a transistor that used the fuel from our cells (a molecule called ATP). And now, a French team has announced the development of a fuel cell that can use the glucose (sugar) inside an animal to produce electricity. Their paper is available free at the journal PLoS One.
The team surgically implanted the device in the abdominal cavity of two rats. The maximum power of the device was 6.5 microwatts, which approaches the 10 microwatts required by pacemakers [Technology Review].
Philippe Cinquin and his team created the cell, in which graphite electrodes are coated with enzymes that oxidize glucose to produce energy. Then connectors carry the electricity from the cell to whatever it’s powering.
The structure of Aleksandr Noy’s new transistor is unimpressively simple: just a carbon nanotube connecting two metal electrodes. But what makes it special is what he and his team use to control it: adenosine triphosphate (ATP), the fuel from our own cells. The project, published in a study in Nano Letters, achieves a key step in unifying man and machine.
The way it works: An insulator coats the ends of the nanotube, but not the middle—it’s left exposed.
The entire device is then coated again, this time with a lipid bi-layer similar to those that form the membranes surrounding our body’s cells [New Scientist].
Finally, the team poured a solution of ATP plus potassium and sodium across the transistor. That created an electric current, one that was stronger the more ATP they poured.
The magic is in the lipid bi-layer, which contains an ATP-sensitive protein that serves as a kind of ion pump when ATP is present. The lipid hydrolyses ATP molecules, with each occurence causing three sodium ions to move one way through the lipid and two potassium ions to move the other way, netting one charge across the bi-layer to the nanotube [Popular Science].
Noy claims to have created “the first example of a truly integrated bioelectronic system,” New Scientist says. And as simple as the transistor is, the idea behind it—harnessing the energy already in our bodies to power electronics—will be one of the keys to creating battery-free devices that monitor our cells, connect to our brains, or do things we won’t think of until we’ve (finally!) got nanodevices hooked up to our brains.
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Image: Aleksandr Noy et. al.