An advanced in situ imaging method using heavy metal-doped hollow tubes to evaluate the biokinetics of carbon nanotubes in vivo

The biosafety of carbon nanotubes (CNTs) is a concern, and CNT biokinetics is a key biosafety issue. CNTs labeled with carbon isotopes, functionalized with moieties, or coated with colloidal metal particles have been used to monitor CNT biokinetics, though major technical issues (such as isotope preparation and handling or change in CNT surface properties) remain. The present report aims at establishing an advanced and simple in situ imaging method of CNTs monitoring in vivo involving the use of CNTs filled with heavy metal particles (peapods). Gadolinium (Gd)-peapods containing GdCl 3 were synthesized using double-walled CNTs. The limits of Gd-peapods detection on magnetic resonance imaging (MRI) in solutions and agarose gel cubes were 1.3 μg ml −1 and 4 μg ml −1 , respectively. The peapods in rats was easily visualized by MRI and the change in signal intensity was dose dependent. This newly developed method can be used to monitor CNT biokinetics in vivo without tedious tissue preparation.