Living Cells Get Nanosurgery

Using microscopic lances to remove material from fertilized eggs is now a routine technique. But these microcapillaries are still quite clumsy and difficult to control precisely without damaging the cell. As they press through the cell wall, it is often deformed so badly that the cell dies.

Now, Japanese researchers have turned an atomic force microscope (AFM) into a surgical tool for cells that could add or remove molecules from precise locations inside a cell without harming it.

The team used a beam of energetic ions to sharpen a standard silicon AFM tip into a needle just eight micrometres long and 200 nanometres wide.

When the researchers inserted the needle into a human embryonic kidney cell, the cell wall was indented by only 1 micrometre. That's much more delicate than comparable microcapilliary procedures, they say.

The cell membrane quickly returned to its original shape, and the needle was pushed into the cell's nucleus. The researchers claim this is the first time that solid material has been inserted into a nucleus of a living cell so accurately.

The needle will allow researchers to inject molecules into specific regions of a cell, says Saul Tendler, a biophysicist at Nottingham University, UK, who uses AFM to investigate biological systems. For example, strands of DNA could be inserted directly into the nucleus to test new gene therapy techniques.

It would also be possible to monitor the chemistry of a cell in real time, Tendler adds, by coating the needle's tip with molecules that grab onto chemicals produced inside the cell. If the tip were designed to fluoresce when the molecules bind, or to change its electrical charge in a detectable way, scientists could watch the cell's response to a new drug, for example.