The application of magnetic nanoparticles in the treatment and monitoring of cancer and infectious diseases

Since the manufacture and use of nanoparticles are increasing, humans are more likely to be exposed occupationally or via consumer products and the environment. However, so far toxicity data for most manufactured nanoparticles are limited. The aim of this study was to investigate and compare different nanoparticles and nanotubes regarding cytotoxicity and ability to cause DNA damage and oxidative stress. The study was focused on different metal oxide particles (CuO, TiO2, ZnO, CuZnFe2O4, Fe3O4, Fe2O3), and the toxicity was compared to that of carbon nanoparticles and multiwalled carbon nanotubes (MWCNT). The human lung epithelial cell line A549 was exposed to the particles, and cytotoxicity was analyzed using trypan blue staining. DNA damage and oxidative lesions were determined using the comet assay, and intracellular production of reactive oxygen species (ROS) was measured using the oxidation-sensitive fluoroprobe 2',7'-dichlorofluorescin diacetate (DCFH-DA). The results showed that there was a high variation among different nanoparticles concerning their ability to cause toxic effects. CuO nanoparticles were most potent regarding cytotoxicity and DNA damage. The toxicity was likely not explained by Cu ions released to the cell medium. These particles also caused oxidative lesions and were the only particles that induced an almost significant increase (p = 0.058) in intracellular ROS. ZnO showed effects on cell viability as well as DNA damage, whereas the TiO2 particles (a mix of rutile and anatase) only caused DNA damage. For iron oxide particles (Fe3O4, Fe2O3), no or low toxicity was observed, but CuZnFe2O4 particles were rather potent in inducing DNA lesions. Finally, the carbon nanotubes showed cytotoxic effects and caused DNA damage in the lowest dose tested. The effects were not explained by soluble metal impurities. In conclusion, this study highlights the in vitro toxicity of CuO nanoparticles.

Exchange-spring magnets are nanocomposites that are composed of magnetically hard and soft phases that interact by magnetic exchange coupling. Such systems are promising for advanced permanent magnetic applications, as they have a large energy product--the combination of permanent magnet field and magnetization--compared to traditional, single-phase materials. Conventional techniques, including melt-spinning, mechanical milling and sputtering, have been explored to prepare exchange-spring magnets. However, the requirement that both the hard and soft phases are controlled at the nanometre scale, to ensure efficient exchange coupling, has posed significant preparation challenges. Here we report the fabrication of exchange-coupled nanocomposites using nanoparticle self-assembly. In this approach, both FePt and Fe3O4 particles are incorporated as nanometre-scale building blocks into binary assemblies. Subsequent annealing converts the assembly into FePt-Fe3Pt nanocomposites, where FePt is a magnetically hard phase and Fe3Pt a soft phase. An optimum exchange coupling, and therefore an optimum energy product, can be obtained by independently tuning the size and composition of the individual building blocks. We have produced exchange-coupled isotropic FePt-Fe3Pt nanocomposites with an energy product of 20.1 MG Oe, which exceeds the theoretical limit of 13 MG Oe for non-exchange-coupled isotropic FePt by over 50 per cent.