The discovery made by a team at Yale University [Fahmy et al., Langmuir (2010) 26, 5645 doi: 10.1021/la902068z] could be exploited in adoptive immunotherapy in the treatment of cancer.

Previously, the Yale team discovered that defects in carbon nanotubes have an unexpected effect on the activation of particular white blood cells, the immune system's T cells. When T cell antigens are added to the surface of the nanotubes they trigger T cell production far more effectively than coating other substrates, traditionally used in research, such as polystyrene, even though the antigen count remains the same between systems. The team has now explained this seeming paradox, which they say could lead to a new approach to adoptive immunotherapy.

However, it was when the team added a functional layer to single-walled carbon nanotubes by treating with nitric acid and lithium borohydride, that their potential was revealed. Functionalisation results in nanotubes with hydroxyl end groups that have an enhanced capacity to adsorb proteins. The treatment also has the added advantage of rendering the nanotube bundles non-toxic in T cell culture, even up to 150 micrograms per millilitre.

“Carbon nanotube bundles resemble a lymph node microenvironment, which has a labyrinthine geometry,” explains Tarek Fahmy. “The nanotube bundles seem to mimic the physiology and adsorb more antigens, promoting a greater immunological response.”

This phenomenon could be put to good use. In the current approach to adoptive immunotherapy, T cells are extracted from a patient's blood and cultivated in the laboratory using an antigen to encourage the T cells to form clusters which can then be transferred back into the patient. This circumvents the fact that the natural production of tumour-fighting T cells in the body is usually suppressed by the tumour. Clustering is the key, the more an antigen is clustered, the more effective the therapy once the clusters are administered to the patient.

The approach is slow and laborious, taking weeks to produce adequate cluster sizes. Fahmy's nanotube approach is three times as fast, which could cut delays in treatment significantly. The team is now working on a method for removing the nanotube substrate before re-administering the T-cell enhanced blood to avoid the risk of side-effects.