Biocompatibility of Dextran-Coated 30 nm and 80 nm Sized SPIONs towards Monocytes, Dendritic Cells and Lymphocytes

Dextran-coated superparamagnetic iron oxide nanoparticles (SPION(Dex)) of various sizes can be used as contrast agents in magnetic resonance imaging (MRI) of different tissues, e.g., liver or atherosclerotic plaques, after intravenous injection. In previous studies, the blood compatibility and the absence of immunogenicity of SPION(Dex) was demonstrated. The investigation of the interference of SPION(Dex) with stimulated immune cell activation is the aim of this study. For this purpose, sterile and endotoxin-free SPION(Dex) with different hydrodynamic sizes (30 and 80 nm) were investigated for their effect on monocytes, dendritic cells (DC) and lymphocytes in concentrations up to 200 µg/mL, which would be administered for use as an imaging agent. The cells were analyzed using flow cytometry and brightfield microscopy. We found that SPION(Dex) were hardly taken up by THP-1 monocytes and did not reduce cell viability. In the presence of SPION(Dex), the phagocytosis of zymosan and E. coli by THP-1 was dose-dependently reduced. SPION(Dex) neither induced the maturation of DCs nor interfered with their stimulated maturation. The particles did not induce lymphocyte proliferation or interfere with lymphocyte proliferation after stimulation. Since SPION(Dex) rapidly distribute via the blood circulation in vivo, high concentrations were only reached locally at the injection site immediately after application and only for a very limited time. Thus, SPION(Dex) can be considered immune compatible in doses required for use as an MRI contrast agent.