“Since tissues in our body possess nanostructured topographies, we could use nanophase materials to improve tissue regeneration,” Tom Webster of Purdue told nanotechweb.org. “Carbon nanofibres/nanotubes can provide such a biologically active topography while at the same time offering exciting mechanical and electrical properties for bone/neural implant applications.”

Webster and colleagues tested composites made of carbon nanofibres with a diameter of about 60 nm in a matrix of polycarbonate urethane, a polymer that is already approved for use in the body. They used samples with nanofibre volume fractions of 0, 2, 10, 25 and 100%.

“The first step is to determine if cells can function on such materials,” said Webster. “We found that they not only function, but function better than on traditional materials, and better the smaller we make the fibres.”

Neurons (brain nerve cells) cultured on the composite material showed neurite extensions, the first stage in forming axons. According to the scientists, this indicates that the materials can promote the interactions with neurons that are needed for successful neural probes. Composites containing a higher fraction of nanofibres showed decreased adhesion to astrocytes - cells that can impede normal neuron function by creating unwanted glial scar tissue. Altering the fraction of carbon nanofibres in the composite also changed its electrical properties, which could be useful in tailoring the properties of the neural implant.

Similarly, osteoblasts, or bone-forming cells, adhered better to composites with a higher volume fraction of carbon nanofibres. But fibroblasts - cells that synthesize fibrous soft tissue that’s unhelpful on the surface of implants - stuck less readily to composites containing a higher percentage of carbon nanofibres.

“Both neurons and osteoblasts can function on carbon nanofibres and composites containing carbon nanofibres,” said Webster. “This opens the door for the use of these materials in orthopaedic and neural applications. Moreover, cells that traditionally contribute to the failure of these implants do not function well on the carbon nanofibres. This could be a win-win situation.”

Webster says the composite materials could eventually be used as orthopaedic coatings that would enhance new bone growth to fix the implant in situ quickly. The materials could also have applications as neural implants, such as in probes that monitor or regenerate neural tissue electrical activity in damaged areas of the brain.

The researchers reported their work in Nanotechnology.