Ultrasmall magnetic iron oxide nanoparticles (<5 nm) with very uniform size distribution can be also synthesized using the water-in-oil microemulsion method [13].Recently, more sophisticated Fe2O3 nanoparticles were fabricated where the magnetic core was covered by an amorphous silica shell [14]. The frequently used raw materials for Fe2O3/SiO2 preparation are iron salts (chlorides [15], nitrates [16], sulphates [17] etc.) and various silicates (water glass, sodium metasilicate). In the case of the sol-gel preparation technique employing TEOS (tetraethyl orthosilicate) as silica source, it was discovered that the particle size was independent of the silica host matrix porosity, but strongly dependent on the amount of solvent trapped inside the gels [18].

The silica shells could be further modified for better conjugation with various biological molecules such as antibodies, proteins, targeting ligands etc. [19]. From the tumor diseases treatment point of view, �CNH2 and �CSH groups are particularly interesting, because they can provide easy coupling of magnetic nanoparticles with various biologically important molecules such as the promising tumor disease marker called metallothionein [20]. Streptavidin is another important material which can be immobilized on magnetic nanoparticles in order to use them for biosensing purposes [21]. Streptavidin is known for its special affinity towards the vitamin biotin and hence it is suitable for detection of diverse biomolecules in immunoassays, e.g. detection of viral nucleic acids in vitro.

Moreover, it was found that the combination of SiO2 core and protecting coating was useful for designing paramagnetic gadolinium nanoparticles for multimodal contrast agent with optical and magnetic properties [22]. However, the synthesis of such products is often time-consuming, so there is a demand for using Entinostat rather simpler ways of fabricating magnetic nanoparticles. This paper is aimed at the study of basic magnetic properties of silica coated and non-coated iron oxide prepared with the help of a simple co-precipitation method compared to gadolinium nanoparticles in silica matrix fabricated using a water in oil microemulsion system.2.?Experimental SectionTo prepare Fe2O3/SiO2 nanoparticles, we employed an easy co-precipitation method reported previously by Ichiyanagi et al. [23]. Briefly, a 0.

05 M aqueous solution of FeCl2?4H2O (Fluka) was mixed with 0.02 M aqueous solution of Na2SiO3?9H2O (Reachim) at pH 7. The formed black colored precipitate was washed with distilled water, dried at 80 ��C for 15 min and finally air-annealed for 4 hours at 800 ��C in an oven.The following process was applied for the fabrication unmodified Fe2O3 magnetic particles: 0.05 M aqueous solution of FeCl2?4H2O was mixed with a solution containing 1g/L of K2CO3 (Penta) under constant stirring up to pH 7, which resulted in the formation of a black precipitate.