This research was focused on the possibility of iron sensing by means of bacterial cultures. The effect of ferric and ferrous ions on <i>Pseudomonas aeruginosa</i>, which has the ability to uptake the environmental iron in the form of complex iron compositions named siderophores, characterized by luminescent features, was studied. The different sensitivity to the iron from oxide compounds in comparison to the iron from chlorides and sulfate was emphasized by means of fluorescence measurements. It could be stated that <i>Pseudomonas aeruginosa</i>, from human body specimens could be the biological component of an iron biosensor for ferrofluid traces reminiscent after the administration for medical purposes.
Comparative study on the ferrophase dimensional distribution within a water ferrofluid was carried out by applying the atomic force microscopy (AFM) scanning and the transmission electron microscopy (TEM). The ferrophase has a magnetite core prepared by chemical co-precipitation and a double layer coating of citric acid. The diameter histograms revealed the main peak at about 9 nm which is concordant with a high degree of stability of the ferrofluid.