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Inside Information: Nanofibers Deliver DNA to Cells
By Kate Dalke

Scientists looking for new ways to deliver DNA to cells have turned to carbon nanofibers. Like tiny needles, these fibers can be used to inject DNA into the cell nucleus, a process called “microinjection.”

Nanofiber chip with hamster cells on top. In the background, cells injected with nanofibers glow green.

Using an experimental technique, the researchers tethered DNA to carbon fibers, which were then poked into cells in culture. The new technique could potentially be used to inject DNA into millions of cells “in parallel,” rather than one at a time.

The technique could be used to deliver and turn on a gene inside a cell for a controlled period of time. Although the technology is still in its infancy, one application could be a skin patch that would inject drugs or proteins into surface cell.

“When your treatment regimen is complete, simply remove the nanofiber chip, along with its modifying DNA,” says Timothy McKnight, who led the study at the Oak Ridge National Laboratory in Tennessee.

The key to the technique is the fibers. The scientists grew arrays of carbon fibers that stuck straight up off a silicon chip. The fibers are spaced so that when cells are spun down onto the fibers using a centrifuge, each cell is pierced by only one fiber.

“It’s like throwing a bunch of baseballs against of bed of nails,” says McKnight, who adds that the fibers and the cells remain attached to the chip.

“We literally throw the cells onto the fibers, and then smush the cells into the chip to further poke the fibers into the cell,” McKnight continues. The tips of the fibers measure up to 50 nanometers in diameter, which is 50-billionth of a meter.

As a test of the technique, the researchers coated the fibers with a gene for a green fluorescent protein. The gene was turned on in hamster cells, making them glow green.

Adding a gene to a cell would be a one-shot deal in the sense that it would not be passed on to daughter cells. The DNA would be bound to the nanofiber and not available during replication.

Having experimented with animal cells, the researchers plan to microinject bacterial and plant cells. They are also working on ways to detach the fibers and cells from the chip after injection.

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McKnight, T.E. et al. Intracellular integration of synthetic nanostructures with viable cells for controlled biochemical manipulation. Nanotechnology 14, 531-556 (April 9, 2003).

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