Characterization of dextran-coated magnetic nanoparticles (Fe3O4) conjugated with monoclonal antibody through low gradient magnet and centrifugation-based buffer separation processes

Conjugation of magnetic nanoparticles (MNPs) with biomolecules can be achieved through covalent or non-covalent bonding and chemisorption. By glutaraldehyde cross-linking, we successfully conjugated mouse monoclonal antibody (Ab) with amine-functionalized dextran-coated MNPs of diameter 50 nm. We aim to characterize the antibody-conjugated MNPs (Ab-MNPs) after buffer separation through low-gradient magnet and centrifugation. The magnetic separation/washing was achieved throughout the conjugation process by attaching the MNPs solution to a natural magnet for about 12 h. The centrifugation-based separation steps were done at 15,000xg for 30 min. The transmission electron microscope (TEM) data showed the flower-shaped core MNPs and their increased diameter after conjugation with Abs. The nanoparticle tracking analysis (NTA) also revealed the size distribution and drift velocities in MNPs and Ab-MNPs. The size distribution and concentration data showed an increased size and a lower value after conjugation, respectively. The drift velocities of Ab-MNPs prepared by the centrifugation method were significantly reduced than magnetic separation and standard MNPs.