| Materials with specific properties are required for the propulsion of a therapeutic micro-device called Magnetic Resonance Submarine (MR-Sub) in the blood vessels by magnetic gradients generated by a clinical Magnetic Resonance Imaging (MRI) and the design of functional components for this device. This report introduces chosen materials based on a design study of this device, a biocompatibility screening of these materials and different solutions to increase their biocompatibility.; The magnetic materials, ordered by their saturation magnetization, show clearly that the most suitable alloy for the propulsion of the MR-Sub is not a biomaterial. It has been decided to use the iron-cobalt (Fe-Co) alloys. Two alloys have been studied: the Permendur (49%Co, 49%Fe, 2%V) and the Vacoflux 17 (17%Co, 81%Fe, 2%Cr). A cell viability test, called the MTT test, has shown that the Vacoflux 17 is less cytotoxic than the Permendur. The Vacoflux 17 has a higher corrosion potential than the Permendur but the alloy is not able to form a stable protective layer. After these results, a first titanium coating has been done by vapour deposition. The aim of this surface treatment is the protection the alloy surface from the bodily fluids.; The MR-Sub requires the developments of functional components as tweezers, release systems, and targeted therapeutic agents. In this context, a preliminary study of the biocompatibility of smart magnetic materials has been done. Smart magnetic materials are able to change their shape in a magnetic field. Two candidate materials were investigated: the Tb-Dy-Fe (terbium-dysprosium-iron) alloy, a giant magnetostrictive material, known as Terfenol-D and the single crystal Ni-Mn-Ga (nickel-gallium-manganesium) alloy, a magnetic shape memory alloy. The cell viability of the Tb-Dy-Fe is very high after 72 hours incubation time. The Ni-Mn-Ga is cytotoxic after 48 hours incubation time. The Terfenol-D has a poor resistance to corrosion and its degradation is significant. The behavior of the Ni-Mn-Ga in corrosion is not acceptable. Moreover, it is subject to form pits which are very dangerous because of ions release. The most promising way to use these materials for medical applications is the development of biocompatible composites.; The cytotoxicity of Fe-Co magnetic nanoparticles coated with oleic acid has been investigated. These nanoparticles were selected for their high magnetic properties. These nanoparticles can be embedded on the MR-Sub and released in a specific place to make a therapeutic action in targeted area in very small blood vessels. The cell viability is very high after 24 hours of exposure to the nanoparticles. It is possible to track these nanoparticles with a MRI system. |
