The transference into water was performed following a previously reported method with slight modifications . In brief, 225 mg of poly(maleic anhydride-alt-1-octadecene) (PMAO) were added to a flask containing 195 mL of chloroform and placed in an ultrasonic bath for 30 min at room temperature. Subsequently, 10 mgFe/mL in 5 mL of CHCl3 were added dropwise, and the mixture was sonicated for another 15 min. Afterwards, the solvent was slowly removed under vacuum (200 mbar, 40°C). The MNPs were then resuspended in 20 mL of NaOH 0.05 M and rota-evaporated (200 mbar, 70 °C) until complete evaporation of CHCl3. At this point, the solution became clear as MNPs were completely transferred to water. MNPs were then filtered using 0.22 µm syringe filters. To remove the excess of unbound polymer, the MNPs suspension was centrifuged at 24000 rpm for 2 h four times and finally the MNPs were redispersed in milliQ water for further use.