'Nanohorns' could prod immune system into action

Technology 19 June 2008

The immune response triggered by carbon nanotube-like structures could be harnessed to help treat infectious diseases and cancers, say researchers.

The way tiny structures like nanotubes can trigger sometimes severe immune reactions has troubled researchers trying to use them as vehicles to deliver drugs inside the body in a targeted way.

White blood cells can efficiently detect and capture nanostructures, so much research is focused on allowing nanotubes and similar structures to pass unmolested in the body.

But a French-Italian research team plans to use nanohorns, a cone-shaped variety of carbon nanotubes, to deliberately provoke the immune system.


They think that the usually unwelcome immune response could kickstart the body into fighting a disease or cancer more effectively.

Distress signal

To test their theory, Alberto Bianco and Hélène Dumortier at the CNRS Institute in Strasbourg, France, in collaboration with Maurizio Prato at the University of Trieste, Italy, gave carbon nanohorns to mouse white blood cells in a Petri dish. The macrophage cells’ job is to swallow foreign particles.

After 24 hours, most of the macrophages had swallowed some nanohorns. But they had also begun to release reactive oxygen compounds and other small molecules that signal to other parts of the immune system to become more active.

The researchers think they could tune that cellular distress call to a particular disease or cancer, by filling the interior of nanohorns with particular antigens, like ice cream filling a cone.

“The nanohorns would deliver the antigen to the macrophages while also triggering a cascade of pro-inflammatory effects,” Dumortier says. “This process should initiate an antigen-specific immune response.”

Safe shape?

“There is still a long way to go before this interesting approach might become safe and effective,” says Ruth Duncan at Cardiff University, UK. “Safety would ultimately depend on proposed dose, the frequency of dose and the route of administration,” she says.

Dumortier agrees more work is needed, but adds that the results so far suggest that nanohorns are less toxic to cells than normal nanotubes can be. “No sign of cell death was visible upon three days of macrophage culture in the presence of nanohorns,” Dumortier says.

Recent headline-grabbing results suggest that nanotubes much longer than they are wide can cause similar inflammation to asbestos. But nanohorns do not take on such proportions and so would not be expected to have such an effect.

Journal reference: 10Advanced Materials (DOI: 1002/adma.200702753)