DIVERSITY: Nanomaterials are assembled from many different substances and are being used in an increasing number of new practical applications, including in medicine. That means we need to identify potential adverse side effects.

When nanotubes are dangerous

Across the globe, researchers are racing to develop new nanomaterials, and to find ever more applications for them. Many of these new materials are thought to be of great importance in medical diagnostics and treatment.

But the worry is how nanomaterials will behave if they go awry in the body. Horror scenarios include inducing cell death, altering genetic material and developing serious diseases.

A new method, developed at NTNU’s Department of Neuroscience, makes it possible to test how cells react to different nanomaterials. Researchers have looked at different varieties of nanofibres and tubes, and have identified material formulations with different toxicities.

For example, one variant has characteristics similar to the specific asbestos fibre that causes lung cancer.

Hazardous packaging?

One possible application of nanotubes is to develop tailor-made medicine packets, which can be targeted to the area of the body where they need to work. This is one of the hottest research topics worldwide, but also involves many unsolved problems.

A medicine packet is comparable to a mail package. It contains things that must be packaged to withstand the rigours of transportation. The packet must also have a stamp and a clear address so that it arrives at the right place.

In this analogy, the nanotube is the equivalent of the medicine packet container.

“We need to know about side effects and the adverse effects of packaging and what could happen if it ends up at the wrong place, “says Tore Syversen, a professor of neurotoxicology and a leader of the research project.

The method developed by his department will help to sort nanotubes according to their interactions with cells.

Thickness important

Nanomaterials are assembled from many different substances. Some are metal oxides, others are carbon. The carbon-based materials can be designed as fibres or tubes. The difference is in the length: fibres are long and tubes are short. Both are hollow and cylindrical, extremely strong and extremely versatile. For example, they can be bent without breaking.

Syversen’s project has investigated carbon fibres of different compositions. The fibres were added to cell cultures to see how the cells grew and reacted in contact with these nanomaterials.

“We used what are called the endothelial cells from the rat brain. These are cells that lie along the blood vessels in the brain and are very important in determining how substances are transported in and out of the brain. We made this choice because the brain has the strongest ‘filter’ to prevent the intrusion of foreign objects”, Syversen said. These cells proved to be quite sensitive to different types of carbon fibres.

Syversen has found that the diameter of the tubes and fibres is of great importance. Materials may be chemically similar, but they will behave differently depending on their thickness.

Unknown boundary

Professor Syversen makes it clear that the measurement method only gives an indication of potential health effects. The actual effect will be closely tied to how the materials are used – whether they are inhaled, placed on the skin or eaten.

“It is especially important to identify fibres that are similar to asbestos fibres. We already know that these kinds of long and sharp fibres can cause lung cancer – and that means they obviously should not be used in any medical context or other application. Most of the carbon fibres in question will not have these properties, but we know too little today about how to draw the line between dangerous and harmless carbon fibres”, adds Syversen.

Precautionary approach

The project is part of the basic research funded by the Research Council of Norway and Norwegian industry, and is based on the precautionary principle. The practice of studying possible unintended health and environmental effects has started to become routine in medical research, and is particularly relevant in the development of medical technology.

But it is not only in the context of medical research that we need to know about the health effects of various nanomaterials. The new materials are used almost everywhere, from the production of cars and airplanes to sophisticated sports equipment, toothbrushes and clothes.

The biggest limitation right now to their use is that these materials are expensive to produce. If production costs can be reduced, we can expect that they will become more prevalent and will be found in an increasing number of common applications.

By Synnøve Ressem