Functionalization of carbon nanotubes
for potential nanobiotechnology applications

Paris, April 30, 2003

CEA/CNRS Joint Press Release

Teams of chemists from the CEA¹ and the CNRS² recently developed a simple and efficient procedure for making functional carbon nanotubes. This achievement offers prospects for interesting applications in the field of nanobiotechnology, such as the utilization of these molecular structures for the transport of water-insoluble molecules (for example, certain drugs), their use as biosensors, etc. These findings appear in the May 2, 2003 issue of the journal Science.

Carbon nanotubes are carbon cylinders made up of one or more rolled-up graphene sheets, closed off at either end by half-spheres in the shape of a soccer ball. The length of these one-dimensional molecules is around 1 µm (one millionth of a meter) and their diameter varies from one to several nanometers (millionths of millimeter), depending on the number of tubes rolled up together. These carbon nanotubes possess excellent mechanical, structural, and electrical properties, which make these materials valuable for a number of nanotechnology applications, in particular in the field of nanobiotechnology.

Carbon nanotubes are insoluble in organic solvents and water, which today considerably limits the scope of their utilization. Nonetheless, when carbon nanotubes are mixed and agitated with a detergent, they disperse to create a stable suspension. The teams of CEA and CNRS chemists used electron microscopy to analyze the molecular organization that enables these nanotubes to become soluble in the presence of detergents: the molecules of detergent aggregate at the surface of the nanotubes and arrange themselves in the shape of rings and helices. The stability of such assemblies is, however, limited.

In order to determine whether other lipid molecules could adsorb and self-organize on carbon nanotubes, creating more stable assemblies, the researchers designed and synthesized new reagents, which form lipidic "rings" made up of supramolecular half-cylinders (see diagram below). Their stability depends on the length and number of the carbon chains of the lipid reagents of which they are composed. These rings also make it possible to fix proteins onto the surface of the nanotubes.

Creating such stable organic assemblies offers a simple and efficient method to make nanotubes functional using chemical reagents. The supramolecular structure that is thereby obtained may lead to a number of applications in the field of nanobiotechnology: it could be used for the development of molecular sensors (biosensors) for detecting the body's molecules. This structure could also make it possible to create new vectors of hydrophobic components, in particular complex drugs.

Reference: Supramolecular self-assembly of lipid derivatives on carbon nanotubes - Cyrille Richard, Fabrice Balavoine, Patrick Schultz, Thomas W. Ebbesen, Charles Mioskowski – Science, May 2, 2003.

1 - "Service de marquage moléculaire et de chimie bioorganique," Department of molecular labeling and bioorganic chemistry, CEA/Saclay.
2 - "Laboratoire de chimie bioorganique," Laboratory of bioorganic chemistry, CNRS – Université de Strasbourg 1.