Sample Zeta potential (mV) Hydrodynamic diameter (nm) MNP -44.3 ± 0.7 91.2  ± 7.5 Pre-activated MNP -36.6 ± 0.8 135.5 ± 8.2 Covalent MNP-N6L(6 µmol N6L/g Fe) -30.2 ± 1.2 193.3 ± 19.1

Table 1: Zeta potentials and hydrodynamic sizes of MNP at pH 7.5. Each value presented is the average of 3 measurements. The error on zeta potentials is the standard deviation on the 3 measurements and the error on hydrodynamic sizes is the average polydispersity index (PDI) over the 3 measurements.