Carbon Nanotubes Could Be Used against Tumors

Carbon nanotubes possess amazing properties propelling them in the front of nanotechnology experimentations.

Now, a team led by Dr. Hongjie Dai, at the Center for Cancer Nanotechnology Excellence Focused on Therapy Response (CCNE-TR), based at Stanford University, have proven that single-walled carbon nanotubes (SWCNTs) wrapped in polyethylene glycol (PEG), can be used with ease to destroy target tumors in living animals.

The CCNE-TR team wrapped commercially available SWCNTs with PEG, which is a biocompatible polymer often used in drug delivery applications to increase circulation lifetimes and water solubility.

The researchers employed PEG of two different lengths, in order to achieve coated SWCNTs of 1 nanometer in diameter/100 nm in length and 5 nm in diameter/300 nm in length.

To the coated nanotubes, the scientists bound a tumor-targeting peptide named cyclic-RGD to the end of the PEG chains.

RGD (formed by the amino acids called arginine, glycine, and aspartic acid) attaches to the protein ævß3, which is encountered on the surface of certain types of cancer cells.

Each nanotube carries multiple cyclic-RGD targeting molecules.

To monitor the nanotubes inside the body of living animals, the scientists also bound to the PEG molecules multiple copies of DOTA, a chemical that will attract various metal ions.

In the current research, the DOTA molecules were sensitive to a radioactive isotope of copper, 64Cu, which can be tracked using positron emission tomography (PET).

Stability tests proved that all of these add-ons stayed firmly bound to the nanotubes even after heating them to 70°C for more than one week.

Mice bearing tumors that express ævß3 on their surfaces were injected with a solution of this nanotube and the team tracked with PET the nanotubes over the next 24 hours.

10-15 % of the SWCNTs coated with the larger PEG chains accumulated within tumors, with a maximum intake within 6 hours after injection, while only 3 to 4 % of the nanotubes coated with the smaller PEG chains targeted the tumors.

SWCNTs were detected inside the tumors through Raman spectroscopy, which can pick the unique optical signals emitted by these nanotubes.