Implants

Implants can perform a number of different functions: from joint replacement, to stents which keep arteries open, to active implants such as cardiac pacemakers and cochlear implants (to restore hearing loss). In all cases such implants must interact closely with biological tissues. One of the key issues is encouraging the patient’s cells to stick to the implant where required (e.g. for bone grafts) thus assisting in the repair of a damaged tissue, while in other cases ensuring that no cell or biological material sticks (such as the interior of arterial stents).

Over the last few years it has become clear that both chemical signals and physical characteristics of materials effect the ability of cells and biomiolecules to stick. For example, nanoscale bumps and grooves can increase cell adhesion, whereas completely smooth surfaces are very poor at allowing cells to stick. Decorating surfaces with similar molecules to those that are found in tissues also increases “stickiness”. The applications are seen for example in titanium bone implants that have a coating of nanostructured titanium dioxide which improves integration in the bone, and diamond-like coating of stents and catheters which are smooth and have marked decrease adhesion of blood proteins and cells.