Nanotech News

July 5, 2005

Magnetic Nanotubes Aid Separation and Drug Delivery

Over the past several years, silicon nanotubes have become attractive starting materials for creating multifunctional nanodevices, largely because the inside and outside of the nanotube can be modified independently of one another. Now, researchers from the University of Maryland have used this characteristic to create multifunctional magnetic nanotubes that can be used in bioseparations and as drug delivery vehicles.

In a short communication published in the Journal of the American Chemical Society, Sang Bok Lee, Ph.D., and his colleagues describe a method for coating the inside surface of silicon nanotubes with a layer of iron oxide nanoparticles. Transmission electron microscopic studies of these nanotubes - the researchers made both 60-nanometer-diamter and 200-nanometer-diamter tubes - clearly show that the magnetic nanoparticles coat the inner surface only. The resulting nanotubes display the same magnetic characteristics as magnetic silica nanoparticles.

To demonstrate the utility of these magnetic nanotubes, the investigators used them to remove dye molecules from an aqueous solution. The red dye molecules readily enter the nanotubes, where hydrophobic interactions - the attractive force between two molecules that like to avoid water - hold them in place within the tube structure. The dye-laden nanotubes were then removed from solution with a magnet. This procedure removed more than 95 percent of the dye molecules, leaving the resulting solution almost transparent and clear. The dye was recovered from the nanotubes with a simple solvent extraction. A similar experiment, in which the nanotubes were first labeled with a human antibody, showed that they could be used to purify a biomolecule using a magnetic field. The investigators also presented data showing that they could load various drugs, including the anticancer agent 5-fluorouracil, into the pores of the magnetic nanotube. Release rates are determined by the chemical composition of the nanotube's inner surface.

This work is detailed in a study titled "Magnetic nanotube for magnetic-field-assisted bioseparation, biointeraction, and drug delivery." An abstract is available on the journal's website.
View abstract.