Spinning Carbon Nanotubes Open Pores In Cancer Cells

Under a rotating magnetic field, carbon nanotubes form spinning bundles that drill into cell membranes, researchers have discovered (Nano Lett., DOI: 10.1021/nl301928z). The technique could create pores in tumor cells to destroy them or deliver drugs to them, its inventors say.

Dun Liu, a doctoral student in Alfred Cuschieri’s laboratory at the University of Dundee, in the U.K., knew that carbon nanotubes align parallel to an applied magnetic field. To test how a rotating field would affect nanotubes, he used electron microscopy to observe the nanotubes forming rotating bundles while under such a magnetic field.

Since he knew that individual nanotubes could penetrate cell membranes, he and his colleagues wanted to investigate the interaction of the spinning nanotubes with cells. So they put nanotubes coated with a biocompatible polymer into a culture of breast cancer tumor cells along with a fluorescent dye. The researchers then took three samples of the cells and applied a rotating magnetic field, with strength of either 20, 40, or 75 millitesla, for 20 minutes.

Compared to cells in the lower fields, more cells took up the dye when exposed to higher fields: up to 25% for the 75-millitesla field. Within 24 hours of exposure to the two higher fields, about one-third of the cells died. The researchers used atomic force microscopy to find that exposure to the nanotubes and magnetic fields made the cell surfaces rough.

The researchers speculate that at 40 millitesla, the tubes drill pores in the cells that can quickly reseal, making the cells more permeable but not killing them. At even higher fields, the nanotubes might destroy the cell membranes or create larger pores, the researchers think, so that the cells’ components leak out, killing the cells.

The technique should affect healthy cells in the same way, says Cuschieri. To selectively kill tumors, he imagines using MRI to visualize a tumor so that doctors could inject nanotubes into the cancerous tissue before applying the rotating magnetic field.