Design of the functionalized magnetic nanoparticles (MNP). a The maximum amount of doxorubicin (DOX) loaded electrostatically, keeping the colloidal stability of the MF66 MNP, was 40 μmol/g Fe. MF66, redispersed at 2.4 mg Fe/ml, gave a final concentration of DOX of 96 μM. b The maximum amount of Nucant multivalent pseudopeptide (N6L) loaded electrostatically, keeping the colloidal stability of the MF66, was 4 μmol/g Fe. c To quantify the amount of N6L effectively adsorbed onto the MF66, N6L-AF546 fluorescent variant was used to monitor the unbound N6L-AF546 recovered in the washes by fluorescence. When 4.1 μmol N6L-AF546 per 1 g Fe was added the yield of immobilization was above 98%, obtaining a final amount of 4 μmol N6L-AF546/g Fe. d Multifunctionalization of MF66 was achieved following a sequential procedure. First, DOX was immobilized onto the surface of MF66 using the same protocol described above. Then, N6L was added over MF66-DOX leading to the formation of bifunctional MNP. Multifunctionalized MNP with both DOX and N6L were re-dispersed at 2.4 mg Fe/ml leading to concentrations of DOX = 96 μM and N6L = 9.6 μM.