Nanotube Needles Deliver Quantum Dots

Multiwalled carbon nanotubes can be used as nanoinjectors to deliver quantum dots inside cells, a technique that could enhance studies of cellular processes (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0700567104).

Chemistry professor Carolyn R. Bertozzi, chemistry graduate student Xing Chen, physics professor Alex Zettl, and physics postdoc Andras Kis at the University of California, Berkeley, and Lawrence Berkeley National Laboratory created the devices by first connecting a single nanotube to an atomic force microscope tip. A quantum dot is attached to the nanotube by a linker that has a pyrene moiety at one end, a biotin moiety at the other end, and a disulfide bond in the middle. The pyrene adsorbs to the nanotube, while the biotin binds to streptavidin on the surface of the quantum dot.

As the nanotube needle pokes through a cell membrane, the reducing environment of the cytosol cleaves the disulfide bond, which releases the quantum dot inside the cell. The researchers used single-particle tracking methods to follow quantum dots injected into human cells. This delivery method doesn't require the use of carrier solvents and appears not to physically harm the cells, they note.