For scientists, as for everybody else, it helps to see what’s happening. This is hard to do in the nucleus of a living cell. Standard techniques for watching the activity within the nucleus use dyes or protein markers. These work but tend to flood the nucleus with large molecules and disrupt the chemical activity. Recent research [Zhao, et al. 2010] has demonstrated that using quantum dots to deliver a staining agent to the nucleus is a better option. However, none of these techniques provide targeting capability within the nucleus.
As is often the case, a better tool improves the science. Min-Feng Yu, professor of mechanical engineering at the University of Illinois (Champaign-Urbana, USA) and colleagues studied the problem and constructed what they call a nanoneedle. As the ‘nano’ implies, this needle is a single nanotube 50 nanometers wide. How small is that? A nanometer is roughly 1/100,000 the diameter of a human hair. The 50 nanometer tube is only a few molecules in width. It’s coated with a very thin layer (as in atoms) of gold to create a nanoscale electron probe. The tube is loaded with specialized quantum dots, nanoscale semiconductor particles that will adhere to parts of the nucleus and fluoresce brightly under a standard fluorescent microscope.
The nanoneedle is inserted into the cell and then into the nucleus. It’s so thin, that it passes through the cell and nucleus membranes without damaging them. Inside the nucleus a tiny electrical pulse changes the charge of the tube and the quantum dots are expelled. The key here is precision. As the researchers put it:
“We can insert the nanoneedle in a specific location and wait for a specific point in a biologic process, and then release the quantum dots. Previous techniques cannot do that,” said Yu.
Because the needle is so small, it can pierce a cell with minimal disruption, while other injection techniques can be very damaging to a cell. Researchers also can use this technique to accurately deliver the quantum dots to a very specific target to study activity in certain regions of the nucleus, or potentially other cellular organelles.
[Source: University of Illinois]
In a way, this is an obvious advance: If you want to properly study DNA and nucleic activity at the molecular scale (preferably while the cell is still alive), then you need tools that operate at the molecular scale – nanotools. Of course, nanotools are easier to describe than make. Now that the nanoneedle has been developed, Yu and other colleagues will refine it. It can be used as a mechanical probe, an electrode, and as a delivery system (needle). All three uses could have many applications in cell biology.
The nanoneedle is described in the October 4, 2010 issue of the journal Small Electrochemically Controlled Deconjugation and Delivery of Single Quantum Dots into the Nucleus of Living Cells