ABSTRACT
Particles of various sizes and composition are widely spread in our world. Nanoparticles are released in
the environment by the traffic, by volcanos, or as plant pollen (Figure 29.1). Although, there is no
common definition for nanotechnology, an upper limit of 100 nm size is commonly accepted as
criterion. Thus, nanoparticles are objects in the size between 1 and 100 nm. However, viruses, protein
complexes such as the nuclear core complex [1], and lipid vesicles such as naturally occurring nano-
particles are also in this size range. The intention of this book is to present and discuss the impact of
nanotechnology in medicine, where, in this chapter, the applications of artificially produced iron oxide
nanoparticles are reviewed. Less known, however, is the fact that ferric oxide nanoparticles are naturally
occurring in homing pigeons where magnetite nanocrystals of 1 to 5 nm mean diameter form clusters of
1 to 3 mm which are associated with nervous system [2] and ferric oxide nanoparticles are also found in
many organisms [3]. Further, magnetite material in concentrations of 14 to above 300 ng=g tissue has
been found in heart, spleen, and liver of human dead bodies. The presence of magnetic material in these
organs indicates functions of biogenic magnetite in the human body [4].
