Over the past two years, researchers have demonstrated repeatedly that certain types of carbon nanotubes are among the most effective materials known for transporting proteins, genes, and drug molecules across the cell membrane.
Now, an attempt to better understand this process has found that virtually any type of carbon nanotube can enter a wide variety of cell types. Moreover, it appears carbon nanotubes enter cells using more than one mechanism.
Reporting its work in the journal Nature Nanotechnology, a group headed by Kostas Kostarelos, Ph.D., of the University of London; Maurizio Prato, Ph.D., of the University of Trieste; and Alberto Bianco, Ph.D., of the University of Strasbourg, set out to create a wide range of functionalized carbon nanotubes and determine which chemical and structural features of these nanotubes affected uptake by different cell types. The goal of this study was to develop guidelines that would help investigators create the most effective nanodevice for delivering therapeutic agents to specific types of cells.
To the surprise of the researchers, there appeared to be little difference in nanotube uptake, either by type of nanotube or type of cell. Surface charge or chemical constituents attached to the nanotubes had no effect on uptake. Moreover, the researchers were unable to identify a single biochemical mechanism by which the nanotubes were taken up by cells. For example, using chemicals known to block endocytosis, a major mechanism for nanoparticle uptake, had little effect on the uptake of carbon nanotubes even though the investigators had already shown that cells can use endocytosis to take up carbon nanotubes. The researchers note that the unique long-and-thin shape of carbon nanotubes may enable them to enter cells much like a syringe passes through the skin.
This work is detailed in a paper titled, "Cellular uptake of functionalized carbon nanotubes is independent of functional group and cell type." An abstract of this paper is available at the journal's website. View abstract.