The colorful variety of nanoparticles offers numerous attractive opportunities to industry and enthusiastically written technical papers provide the motivation for a rapid implementation of such novel materials into industrial products and therapeutic strategies. The rapidly growing applications of nanotechnology, however, require a detailed understanding of both benefits and risks [1-3]. Particularly magnetic nanoparticles have attracted increasing interest as they might revolutionize current drug delivery and make cancer remission therapy more effective [3, 4]. Successful application strongly relies on a safe implementation that goes along with detailed knowledge of interactions and effects that nanomagnets might impart once entering the body as well as effective strategies for recycling and removing them from the body once the therapeutic action is over. As the application of such nanomagnets is usually in the ng-mg scale, adequate analytical methods need to be developed that exhibit such high resolution and can detect these ultra-low concentrations.
Since most bio-compatible nanomagnets (metallic or oxidic) are based on iron and the background level of iron in most biological fluids (e.g. human blood) is very high, straight forward elemental analytics (degradation of the nanomagnets followed by AAS, ICP-OS or ICP-MS) are impeded. In this study we demonstrate strategies to detect iron based nanomagnets at very low levels. We will discuss strategies based on precious metal spiking, fluorescence, enzymatic analytics and magnetometry in terms of ease of applicability, biocompatibility and detection limits.
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 I.K. Herrmann, R.N. Grass, W.J. Stark, Nanomedicine 4(7), 787-98 (2009).
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