On September 18, 2011, Nature Nanotechnology posted an article entitled “Cell entry of one-dimensional nanomaterials occurs by tip recognition and rotation.” The authors state that materials with high aspect ratio, such as carbon nanotubes (CNT) and asbestos fibers, have been shown to cause length-dependent toxicity in certain cells because these long materials prevent complete ingestion, which frustrates the cell. The authors note that, while “[b]iophysical models have been proposed to explain how spheres and elliptical nanostructures enter cells,” one-dimensional nanomaterials have not been examined. The authors show “experimentally and theoretically” that cylindrical one-dimensional nanomaterials, such as CNTs, enter cells through the tip first. The abstract states:

For nanotubes with end caps or carbon shells at their tips, uptake involves tip recognition through receptor binding, rotation that is driven by asymmetric elastic strain at the tube-bilayer interface, and near-vertical entry.  The precise angle of entry is governed by the relative timescales for tube rotation and receptor diffusion.  Nanotubes without caps or shells on their tips show a different mode of membrane interaction, posing an interesting question as to whether modifying the tips of tubes may help avoid frustrated uptake by cells.