gms | German Medical Science

Superparamagnetic nanoparticles can be used in medicine in vivo as contrast agents and as a drug carrier system for chemotherapeutics. Recently, accurate detection of occult lymph-node metastases in prostate cancer patients could be achieved. A new approach in local cancer therapy is performed with Magnetic Drug Targeting (MDT). Starch coated magnetic nanoparticles, ionically bound to mitoxantrone were given intraarterially into the tumor supplying artery and focused in the tumor region with an external magnetic field in rabbits. With this delivery system we could achieve total tumor remissions without negative side effects by the use of only 20% and 50% of the regular systemic chemotherapeutic dosage. Radioactive 59Fe-nanoparticles showed 114 times more activity in the tumor region after MDT compared to the control without magnetic field. Furthermore it could be shown that with this system a high and specific enrichment of the bound chemotherapeutic agent in a desired body compartment (i.e. the tumor) is possible. HPLC-analysis of the chemotherapeutic agent after MDT revealed a 75 times higher concentration of the administered dose in the tumor region compared to the regular systemic administration. The aim of the present study was to investigate non-invasively the distribution of the particles with common imaging techniques. The biodistribution of magnetic nanoparticles after MDT was investigated with a high resolution 3-dimensional x-ray-tomography (CCD Camera, 1024x1024 pixels). The respective tumor tissue was then histologically examined. Futhermore tumor bearing rabbits were examined with a 4.7 Tesla MRI before and after MDT. Quantitative analysis was performed with a multichannel SQUID system based on magnetrelaxometry. X-ray-tomography pictures show, that the whole vascular system of the tumor can be reached by MDT and this was corresponding to the histological examination. The visualisation of the particles with MRI is dose dependent. Magnetrelaxometry of the same tumor region revealed a high concentration of the magnetic nanoparticles in the center (800pT), which coincided with the tumor location. Imaging techniques (x-ray, MRI) offer the opportunity to achieve information about the biodistribution of magnetic nanoparticles after Magnetic Drug Targeting and this could be very important to control non-invasively cancer therapy. Magnetorelaxometry is a sensitive technique to quantify the enrichment of magnetic nanoparticles in specific body compartments.