Proactive Surfaces for Implantable Medical Devices

For medical implants, such as those forming artificial bone joints and cardiovascular components, a common mode of failure is the build up of fibrous tissue on the surface of the material, which the body regards as foreign. This is often termed the foreign body reaction. This reaction is believed to be triggered by physically adsorbed protein denatured by its interaction with the surface of the implant.

We aim to control or eliminate the response by attaching a layer of bioactive protein to the implant using our patented covalent immobilization technology. The protein coating is chosen such that it induces the optimal biological response. Desired responses vary according to the nature and location of the implant. We are exploring the use of protein interfaces to encourage the overgrowth of endothelial cells and to reduce thrombosis for applications in stents and cardiovascular implants. In vitro cell culture experiments and thrombosis assays showed excellent results. This will soon be extended to animal studies in collaboration with researchers at the Royal Prince Alfred Hospital.

For bone contacting implants such as hip and knee joints, we are collaborating with the industry partners Cochlear Ltd and Spinecell Pty Ltd, to develop protein layers which encourage osteoblast adhesion and proliferation.

SEM image of a stainless steel stent coated with our plasma polymer after crimping and expansion. The adhesion is excellent due to an engineered graded interface despite large scale plastic deformation of the stent struts.