University of Illinois researchers developed a nanoneedle that releases quantum dots directly into the nucleus of a living cell when a small electrical charge is applied. The quantum dots are tracked to gain information about conditions inside the nucleus. | Image courtesy Min-Feng Yu
Researchers have been exploring a class of nanoparticles called quantum dots, tiny specks of semiconductor material only a few molecules big that can be used to monitor microscopic processes and cellular conditions. Quantum dots offer the advantages of small size, bright fluorescence for easy tracking, and excellent stability in light.
Getting any type of molecule into the nucleus is even trickier, because it’s surrounded by an additional membrane that prevents most molecules in the cell from entering. Researchers developed a nanoneedle that also served as an electrode that could deliver quantum dots directly into the nucleus of a cell – specifically to a pinpointed location within the nucleus. The researchers can then learn a lot about the physical conditions inside the nucleus by monitoring the quantum dots with a standard fluorescent microscope.
The group coated a single nanotube, only 50 nanometers wide, with a very thin layer of gold, creating a nanoscale electrode probe. They then loaded the needle with quantum dots. A small electrical charge releases the quantum dots from the needle. This provides a level of control not achievable by other molecular delivery methods, which involve gradual diffusion throughout the cell and into the nucleus.
They hope to explore using the needle to deliver other types of molecules as well – DNA fragments, proteins, enzymes and others – that could be used to study a myriad of cellular processes.
“It’s an all-in-one tool,” Wang said. “There are three main types of processes in the cell: chemical, electrical, and mechanical. This has all three: It’s a mechanical probe, an electrode, and a chemical delivery system.”
A membrane-penetrating nanoneedle (also serving as a nanoelectrode) is developed for carrying and rapidly releasing individual quantum dots into the nucleus of a living cell via an electrochemical reaction activated by an electrical pulse. Direct delivery of biological probes into the nucleus with high spatial and temporal precision offers new strategies for the study of biological activity in a living cell.