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). A team led by Carolyn R. Bertozzi and Alex Zettl 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. Then the researchers attach a quantum dot to the nanotube via 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 tracked quantum dots injected into human cells, noting that the delivery method appears to leave the cells unharmed.