Nanotechnology is increasingly a part of our lives, and while it has enormous potential for the effective delivery of medication and fighting cancer, there are concerns about health effects such as toxicity and tissue damage. Now a team of scientists has shown that carbon nanotubes can be broken down by an enzyme found in white blood cells - contradicting the previous belief they are not broken down in the body or nature - and hope this new understanding may lead to a way to render carbon nanotubes harmless in medical applications.

Carbon nanotubes are cylindrical carbon molecules, rolled into a tube with a diameter of only a couple of nanometres (1 nanometre = 1 billionth of a meter) and a length that can range from tens of nanometres up to several micrometers.

They are lighter and stronger than steel and have exceptional heat-conductive and electrical properties, making them ideal for use in engineering and electronics. Their future potential is enormous anywhere weight and strength are an issue for example in the architectural, aerospace, and automotive industries.

Carbon nanotubes also have enormous potential for medical diagnostics and disease treatment however research has shown that exposure in mice can lead to impaired lung function and perhaps even to cancer.

It has long been thought that carbon nanotubes were biopersistent; that is, they would not break down in human tissue or in nature. Scientists have suggested that carbon nanotubes are very similar to asbestos fibers, which are themselves biopersistent and which can cause lung cancer (mesothelioma) in humans a considerable time after exposure.

The enzyme myeloperoxidase (MPO) is used by certain types of white blood cell (neutrophils) to neutralize harmful bacteria.

The study was conducted by by researchers at Karolinska Institutet in Sweden, the University of Pittsburgh and the National Institute for Occupational Safety and Health (NIOSH) as as part of the NANOMMUNE project. The findings showed that MPO also broke down carbon nanotubes into water and carbon dioxide. Carbon nanotubes that had been broken down by MPO no longer no longer caused inflammation in mice. The scientists hope that this new understanding of how MPO converts carbon nanotubes into water and carbon dioxide can be of significance to medicine.

Their findings are published in Nature Nanotechnology.