Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
The purpose of this master’s thesis was to, by the use of nanotechnology, improve material properties of the biomedical polymer Optim™, used as the insulation of pacemaker leads. Improved material properties are required to reduce the extent of fibrous encapsulation of the leads. Today, laser ablation is used to be able to remove the pacemaker lead because of the fibrous tissue, which can cause the lead to adhere to vascular structures. Consequently, the laser ablation results in risks of damaging cardiovascular structures. Moreover, improved material properties are needed to reduce the friction at the surface and enhance the wear resistance. Large wearing occurs between the lead and the titanium pacemaker shell as well as lead against lead and the wearing can result in a damaged insulation, which in turn might result in removal of the device.
To achieve these improved material properties a hierarchically micro- and nanostructured and superhydrophobic surface was fabricated and to enhance the wear resistance, nanocomposites with 1 wt % and 5 wt % added hydroxyapatite nanoparticles were fabricated. The surface structures were fabricated via hot embossing and plasma treatment and were characterised with atomic force microscopy, environment scanning electron microscopy and with contact angle measurements. To evaluate the biological response to the surfaces, adsorption of radioisotope labelled human serum albumin proteins and adhesion of the human fibroblast cell line MRC-5 were studied.
The results show that a superhydrophobic surface, with contact angle as high as 170.0 ± 0.4 °, can be fabricated via hierarchically micro- and nanostructures on an Optim™ surface. The fabricated surface is more protein resistant and cell resistant compared to a smooth surface. The nanocomposites fabricated, especially the one with 5 wt % nanoparticles added, show an enhanced abrasive wear resistance compared to Optim™ without added nanoparticles. In conclusion, a hierarchically micro- and nanostructured superhydrophobic surface of the pacemaker lead seems promising for reducing the extent of fibrous encapsulation and by fabricating a nanocomposite, the abrasive wear damage of the lead insulation can be reduced.
2008. , 94 p.