An enzyme capable of separating nanotubes
This past April, a team of scientists from Ireland, Sweden and the United States has published a study showing that an enzyme found in white blood cells are capable of separating carbon nanotubes. The article is published by the prestigious journal Nature Nanotechnology and is to deny what was being said so far, that carbon nanotubes could not be decomposed by the body or nature.
First we’ll quickly explain the structure of the carbon nanotube. We start from graphene, a flat sheet structure with a hexagonal grid whose vertices is a carbon atom. If we take one of these consist of graphene sheets and rolled up into a tube will have a single carbon nanotube. There are many types of nanotubes depending on the number of concentric layers of different diameters, etc. One of the most important properties of nanotubes is that they are very light and up to forty times stronger than steel as their applications in engineering are many. Moreover, the fact that it has been demonstrated that could be used for drug delivery or sensors in the human body has fired his interest in the world of medicine.
Molecular model of a human enzyme myeloperoxidase (hMPO) decomposing a monolayer carbon nanotube. © Nature Nanotechnology.
Despite these very interesting properties, some studies in which mice exposed to the nanotubes through inhalation or injection resulted in the development of severe inflammation, impaired lung function and even cancer. Another issue on which he insisted, until this study, it was his biopersistence, ie the apparent inability of the human body to remove the body.
The group has shown in his work the human myeloperoxidase (hMPO), which is an enzyme defense system of a type of white blood cells, neutrophils, can get break down walled carbon nanotubes simple, mainly carbon dioxide water. Although the different routes that are held until the products are not yet known, researchers have found that at least there is a way of dividing the nanotubes biologically harmless to human body. Previously the director of this work and others had published another article which had already been shown that the wall of a single carbon nanotube could be biodegraded by catalysis by the enzyme horseradish peroxidase (horseradish peroxidase or HPR), for several weeks , but had not been sufficiently investigated.
Additionally, after demonstrating the effectiveness of the hMPO in the degradation of carbon nanotubes, the team developed a technique to stimulate neutrophils to attack the nanotubes by capturing them and thus put in contact with the enzyme to begin decomposition. It consists of impregnating a sample of nanotubes with few antibodies already known, in this case the immunoglobulin, which is the aim of neutrophils, the latter’s capture and the enzyme begins to break down hMPO nanotubes. After 12 hours 100% of the nanotubes had been degraded compared to 30% of those without antibodies implanted.
The study was conducted by 20 scientists from several institutions and research director Dr. Valerian E. Kagan Department of Environmental and Occupational Health at the University of Pittsburgh (Pennsylvania, USA). It was financed with EUR 3.36 million National Institutes of Health and by the 7th Framework Programme of the European Commission, and has carried out within the project NANOMMUNE for comprehensive assessment of the dangerous effects of nanomaterials design the immune system, coordinated by Professor Dr. Bengt Fadeel Karolinska Institute.
