Magnetic nanoparticles have been investigated for biomedical applications for more than 30 years. In medicine they are used for several approaches such as magnetic cell separation or magnetic resonance imaging (MRI). The development of biocompatible nanosized drug delivery systems for specific targeting of therapeutics is the focus of medical research, especially for the treatment of cancer and diseases of the vascular system. In an experimental cancer model, we performed targeted drug delivery and used magnetic iron oxide nanoparticles, bound to a chemotherapeutic agent, which were attracted to an experimental tumour in rabbits by an external magnetic field (magnetic drug targeting). Complete tumour remission could be achieved. An important advantage of these carriers is the possibility for detecting these nanoparticles after treatment with common imaging techniques (i.e. x-ray-tomography, magnetorelaxometry, magnetic resonance imaging), which can be correlated to histology.

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The search for an ideal bone substitute is ongoing. Multiple osteoconductive bone substitutes are available today. Plaster of Paris (POP) (calcium sulfate) has been used for more than 100 years for treatment of skeletal defects. This implant is compared to a new material, hydroxyapatite/calcium carbonate (HA/CC), in a rabbit tibia model. HA/CC is made from partial conversion of coralline calcium carbonate to hydroxyapatite and has an outer hydroxyapatite layer and an inner calcium carbonate core, a combination that leads to faster resorption than that of pure hydroxyapatite. This study compares the histomorphometric and radiographic properties of POP and HA/CC in a rabbit tibial defect. Both implants preferentially restore bone to the cortex relative to the canal. Plaster of Paris was fully resorbed by 6 weeks both radiographically and histometrically and HA/CC was substantially resorbed by 42 weeks. No significant difference was noted in volume fraction of bone between the two implants at 42 weeks postimplantation. Hydroxyapatite/calcium carbonate is a biocompatible bone graft substitute with a rate of resorption significantly slower than plaster of Paris.