The physical and chemical characteristics of these substrates vary depending on the methods used to synthesize and purify the nanotubes, and in the past it was not clear how these properties affected the response of the biological host. Now, a team from Rutgers University and UMDNJ Robert Wood Johnson Medical School, both in the US, has shown that it is possible to control and therefore enhance specific steps in bone cell growth by fine-tuning the attributes of the films.

The researchers used an ad hoc set-up to prepare carbon nanotube films in which the fine structure and the surface energy of the substrate (image A) could be experimentally controlled. Using a variety of techniques including electron and atomic force microscopy, the researchers found that high surface energy (hydrophilic) films yielded better attachment than low surface energy (hydrophobic) films. In both film types, however, adhesion was maximal on medium roughness surfaces and minimal on smooth surfaces (image B). In contrast, proliferation was not dependent on the surface energy and depended on the fine structure of the film with smooth surfaces yielding maximal proliferation rates.

Different design options

These results underscore a unique feature of carbon nanotube embedded films: their tremendous flexibility. This implies that these nanomaterials could be specifically designed to suit different uses. For example, hybrid devices comprising living cells that are in operative contact with an extracellular planar electrode, such as field effect transistors (image C), might be constructed using high proliferation films. In contrast, high surface energy films might be employed in situations that require good cell-to-substrate attachment, such as bone-prosthesis as well as bone-fracture healing, a problem quite common in the elderly.

More details can be found in the journal Nanotechnology.