*3.1. Magnetic Characteristics of USPION Dispersion per Se*

To determine USPIONs uptake during the experiment with animals, one need to characterise USPIONs dispersion. A volume of 10 μL of the dispersion was dropped to the transparent foil (18 cm long and 4 mm wide) vacuum dried for 1 h and inserted into the straw as described above. The hysteresis curves were measured (Figure 9a) at 2 and 300 K. The curves show no difference in total magnetisation at 2 K compared to 300 K, and the USPIONs dispersion is superparamagnetic with no hysteresis at 300 K, but the tendency to saturation is present. The temperature dependence (Figure 9b) showed that the ZFC curve has a peak with maximum at 260 K, indicating that at room temperature the NPs are superparamagnetic. The FC curve exhibits maximum at 240 K and a plateau at low temperature, which can be ascribed to interparticle interactions.

**Figure 9.** Properties of USPION dispersion per se. (**a**) The mass magnetisation vs. the applied magnetic field measured at 2 and 300 K. (**b**) The mass magnetisation vs. the temperature measured at 4000 A/m applied magnetic field.
