Nanowires as Needles to Poke Molecules into Cells
http://www.technologyreview.com/biomedicine/24347/
Many experiments in biology rely on manipulating cells: adding a gene,
protein, or other molecule, for instance, to study its effects on the cell.
But getting a molecule into a cell is much like breaking into a fortress; it
often relies on biological tricks such as infecting a cell with a virus or
attaching a protein to another one that will sneak it through the cell's
membrane. Many of these methods are specific to certain types of cells and
only work with specific molecules. A paper in this week's Proceedings of the
National Academy of Sciences offers a surprisingly simple and direct
alternative: using nanowires as needles to poke molecules into cells.
Cell needles: Beds of vertical silicone nanowires can act as a method for
delivering molecules into cells. In this falsely colored scanning electron
micrograph, a connective-tissue cell rests on these tiny spikes, which impale
the membrane and allow direct access into the cell.
Credit: Hongkun Park
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Nanowires as Needles to Poke Molecules into Cells
Author Hongkun Park, a professor of chemistry and physics at Harvard
University, says that, in theory, "you can put more or less any molecule in
more or less any kind of cell." If the method proves effective, it could
greatly speed the ability to manipulate cells in a variety of applications,
including stem-cell reprogramming and drug screening.
Park's lab recently discovered that cells can be grown on beds of vertical
silicon nanowires without apparent damage to the cells. The cells sink into
the nanowires and within an hour are impaled by the tiny spikes. Even resting
on this bed of needles, cells continue to grow and divide normally. This
setup makes it possible to directly interface with the cell's interior
through the nanowires. "Since we now have direct physical access, we can
deliver molecules into cells without the restrictions of other techniques
that are available," Park says. He adds that while his lab has found that
many different types of cells seem to accommodate the tiny wires without
negative effects, further studies will be needed to examine whether any
important cell behaviors are affected.
To use the nanowires to deliver molecules, Park's team first treated them
with a chemical that would allow molecules to bind relatively weakly to the
surface of the nanowires, then coated the wires with a molecule or
combination of molecules of interest. When cells are impaled on the
nanowires, the molecules are released into the cells' interior. The chemical
treatment of the wires could potentially be manipulated to control the
binding and release of molecules--releasing them more slowly, for
instance--and the wires can be constructed at different lengths to reach
different parts of the cell. To demonstrate the method's flexibility, the
team used the approach to deliver chemicals, small RNA molecules, DNA, and
proteins into a range of cell types.
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