Recently, researchers from the YUHS-KRIBB Medical Convergence Research Institute (MCRI) at Yonsei University, Korea, reported that cationic magnetic nanoparticles can induce cytotoxic effects on live cells. To prepare charged (aminated and carboxylated) magnetic nanoparticles (MnFe2O4), they modified the hydroxyl group of amphiphilic and non-ionic polysorbate 80 with amine (cationic) and carboxyl (anionic) groups, respectively, using a simple bio-conjugation technique. Subsequently, charged magnetic nanoparticles were prepared using cationic and anionic polysorbates via the nanoemulsion method.

The physico-chemical properties – water stability, morphology, colloidal size, surface charge and T2 relaxivity – of the charged magnetic nanoparticles were assessed to evaluate the potential of the material as an MR imaging probe. In the study, cytotoxicity induced from cellular membrane instability due to charged magnetic nanoparticles was found.

As shown in the figure, the cellular viability of murine macrophages (RAW264.7 cell) decreased as the concentration of magnetic nanoparticles increased. In addition, the researchers carried out atomic force microscope (AFM) analysis to investigate changes in cell membrane softness following exposure to charged magnetic nanoparticles.

Effective stiffness was used as a representative parameter of cell membrane softness. The results demonstrated that the positive charged magnetic nanoparticles were able to disturb the stability of the cell membrane composed of negative charged lipids due to the cell–surface interactions.

To reduce the cytotoxicity and evade unwanted immune system responses, modification with non-ionic or anionic surface charges could be an essential step for the fabrication of biocompatible magnetic nanoparticles. Furthermore, the team believes that the surface charge of magnetic nanoparticles should be considered as the key element for theragnostic applications in clinics.

More information can be found in the journal Nanotechnology.