The organic functionalisation of carbon nanotubes can improve substantially their solubility and biocompatibility profile; as a consequence, their manipulation and integration into biological systems has become possible so that functionalised carbon nanotubes hold currently strong promise as novel systems for the delivery of drugs, antigens and genes.

Carbon nanotubes (CNT) are intensively being developed for biomedical applications including drug and gene delivery. Although all possible clinical applications will require compatibility of CNT with the biological milieu, theirin vivocapabilities and limitations have not yet been explored. In this work, water-soluble, single-walled CNT (SWNT) have been functionalized with the chelating molecule diethylentriaminepentaacetic (DTPA) and labeled with indium (¹¹¹In) for imaging purposes. Intravenous (i.v.) administration of these functionalized SWNT (f-SWNT) followed by radioactivity tracing using gamma scintigraphy indicated thatf-SWNT are not retained in any of the reticuloendothelial system organs (liver or spleen) and are rapidly cleared from systemic blood circulation through the renal excretion route. The observed rapid blood clearance and half-life (3 h) off-SWNT has major implications for all potential clinical uses of CNT. Moreover, urine excretion studies using bothf-SWNT and functionalized multiwalled CNT followed by electron microscopy analysis of urine samples revealed that both types of nanotubes were excreted as intact nanotubes. This work describes the pharmacokinetic parameters of i.v. administered functionalized CNT relevant for various therapeutic and diagnostic applications.