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.
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.