Magnetic nanoparticles in magnetic resonance imaging and diagnostics.

Magnetic nanoparticles are useful as contrast agents for magnetic resonance imaging (MRI). Paramagnetic contrast agents have been used for a long time, but more recently superparamagnetic iron oxide nanoparticles (SPIOs) have been discovered to influence MRI contrast as well. In contrast to paramagnetic contrast agents, SPIOs can be functionalized and size-tailored in order to adapt to various kinds of soft tissues. Although both types of contrast agents have a inducible magnetization, their mechanisms of influence on spin-spin and spin-lattice relaxation of protons are different. A special emphasis on the basic magnetism of nanoparticles and their structures as well as on the principle of nuclear magnetic resonance is made. Examples of different contrast-enhanced magnetic resonance images are given. The potential use of magnetic nanoparticles as diagnostic tracers is explored. Additionally, SPIOs can be used in diagnostic magnetic resonance, since the spin relaxation time of water protons differs, whether magnetic nanoparticles are bound to a target or not.

Secondary radiation-induced bone tumours demonstrate a high degree of genomic instability predictive of a poor prognosis.

Secondary bone tumours arising in the field of a preceding radiotherapy are a serious late effect, in particular considering the increasing survival times in patients treated for paediatric malignancies. In general, therapy associated tumours are known to show a more aggressive behaviour and a limited response to chemotherapy compared with their primary counterparts. It is not clear however whether this less favourable outcome is caused by inherent genetic factors of the tumour cells or by a general systemic condition of the patient. To elucidate this we analysed a series of bone sarcomas with a history of prior irradiation for the presence of genomic alterations and compared them with the alterations identified earlier in primary osteosarcomas. We analysed seven radiation induced bone sarcomas for genome-wide losses of heterozygosity (LOH) using Affymetrix 10K2 high-density single nucleotide polymorphism (SNP) arrays. Additionally, copy number changes were analysed at two distinct loci on 10q that were recently found to be of major prognostic significance in primary osteosarcomas. All the investigated tumours showed a LOH at 10q21.1 with 86% of cases (6/7) revealing a total genome-wide LOH score above 2400 and more than 24% of the genome being affected. Our results indicate similar genetic alterations in radiation induced sarcomas of bone and primary osteosarcomas with a poor prognosis. We speculate that the high degree of genomic instability found in these tumours causes the poor prognosis irrespective of the initiating event.

Improved method for impedance measurements of mammalian cells.

This study describes the use of impedance spectroscopy as a non-invasive tool to monitor cell proliferation and morphology and to obtain better measurements of cell kinetics. The goal was to determine test frequencies at which the cell behaviour towards different chemicals and toxins can be monitored with good time resolution. For optimisation of the test frequency it is in the first instance necessary to measure an impedance spectrum of the confluent cell layer. Secondly, the frequency of the highest peak in the spectrum will be determined and further experiments will be carried out at this fixed test frequency. In contrast to measurements at the mainly used 10 kHz (33%), signal differences between a confluent cell layer and cells after treatment with 0.2% Triton X-100 of up to 60% were obtained. In this work the measurements were carried out using interdigitated electrode structures (IDES) on a glass substrate. Impedance spectra of confluent L929 and MDA cell layers were obtained with the Solartron response analyzer.