Fig. 4

Characterization of physical properties of EGFR-SPIO nanoparticles and validation of antibody-SPIO conjugation. a Size distribution of EGFR-SPIO, unconjugated lipid SPIO, and non-coated SPIO nanoparticles were determined through DLS measurement. The size of EGFR-SPIO peaked at 16.34 ± 0.0 nm on volume distribution graph and that of unconjugated lipid SPIO nanoparticles peaked at 10.59 ± 1.27 nm. The non-coated SPIO aggregated and measurement peaked above 1000 nm. b TEM image of EGFR-SPIO nanoparticles. Scale bar, 10 nm. c Zeta potential statistics graph of EGFR-SPIO nanoparticles. The zeta potential of EGFR-SPIO nanoparticles peaked at − 9.24 ± 0.43 mV. d The stability of EGFR-SPIO conjugates was evaluated by measuring the variation of size through DLS. The indicated nanoparticles diluted in PBS (1:12) were incubated for 0, 0.25, and 3 h at room temperature before subjecting to DLS size measurement. The peak of volume distribution from each time point was measured and averaged, and the % of volume incensement after the cetuximab conjugation on lipid SPIO was calculated. The results indicate that EGFR-SPIO nanoparticles were stable over the observation period at room temperature. e Band shift assay of EGFR-SPIO conjugates. Unconjugated lipid SPIO and EGFR-SPIO nanoparticles were subjected to electrophoresis on 1% agarose gel in TAE buffer. Arrowhead, migration direction; −, cathode; +, anode