Institution: The University of Cambridge
Investigators: Dr Osa Emohare, Professor Neil Rushton
Stream: MPhil
Topic: Biomaterials
Status: Completed
Introduction
The advent of nanotechnology has generated materials that are of interest as a result of both their mechanical properties and size. One of these materials are carbon nanotubes. They are both strong and lightweight and therefore offer the potential for improving the mechanical properties of implant materials.
Although implants made solely of carbon nanotubes may still be a distant prospect, reinforcing pre-existing implant materials such as hydroxyapatite may provide a means by which current performance can be improved.
While important for encouraging bone in growth and performing well in compression, there is a caveat to the use of hydroxyapatite: being a ceramic, it can be brittle in tension. The use of a material in combination with hydroxyapatite that improves its tensile properties may therefore be very attractive.
In addition, carbon nanotubes have very impressive wear characteristics. The majority of current orthopaedic implants that have weightbearing components use high molecular weight polyethylene as part of their weightbearing surface. The combination of polyethylene with carbon nanotubes may also provide an enhanced weightbearing surface for orthopaedic implants.
The potential advantages of nano scale materials are apparent. As tissue engineering is focussed on the regeneration of tissue, the assessment of carbon nanotube and carbon nanotube based composites is also a prelude to the development of resorbable nano scale materials.
The assessment of cell interaction with these materials is of paramount importance because tissue repair and regeneration is based on the premise that the materials used are not only non-toxic to cells, but may also promote cell adhesion, proliferation and differentiation.
Hypothesis
It is, therefore, hypothesised that carbon nanotubes and carbon nanotube based composites may provide a surface which can encourage the attachment, proliferation and differentiation of osteogenic cells.
Materials and Methods
Materials to be used in this study can be broadly classified into three groups:
i. Carbon Nanotubes
ii. Carbon Nanotube/Hydroxyapatite composites
iii. Carbon Nanotubes/ High Density Polyethylene Composites
A range of carbon nanotube modifications will be incorporated into the work. This will enable an assessment of the effects of nanotube diameter and functionalisation.
Cell adhesion, proliferation, differentiation and toxicity will be assessed by means of commercially available standardised assays.
The main type of cells to be used for this work are human bone marrow stromal cells, although inflammatory cells such as monocytes will be used, where relevant, especially in the assessment of toxicity, by the release of lactate dehydrogenase (LDH).
Endpoint
At the end of this study, we envisage that we would have identified the optimum factor associated with the most favourable osteogenic cell function, on both carbon nanotubes and carbon nanotube based composites. This will direct the synthesis of composites that would be best suited for in vivo implantation.
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