Formation of Protein Corona on Rhodium Citrate-Functionalized Magnetic Nanoparticles and Their Interaction with Human Macrophages

Nanoscience and Nanotechnology enable innovations for Medicine and for Biomedical Science. Among the current nanoparticles, maghemite associated with rhodium citrate (Magh-RhCit) has been shown to be promising, because it reduces side effects of drugs while maintaining cytotoxicity for tumor cells. However, NPs in contact with biological fluids are immediately coated by proteins (protein corona) that are unique to each nanomaterial. In this study, the adsorption of the most abundant binding proteins was studied in vitro using a three-step analysis: (1) characterization of the magnetic fluid (Magh-RhCit) before and after incubation with serum; (2) identification and physical and biochemical analysis of protein corona; and (3) the cellular internalization of these nanoparticles in human macrophages. Magh-RhCit was initially obtained in the magnetite phase (Fe3O4) via alkaline coprecipitation of Fe2+ and Fe3+ ions and subsequently oxidized to maghemite by the bubbling of oxygen gas in the suspension. Later, rhodium citrate was associated with nanoparticles. Dynamic Light Scattering data were used for characterization of the hydrodynamic diameter and zeta potential. The morphological characterization and measurement of the particles were obtained from Scanning and Transmission Electron Microscopy, and the X-ray Diffraction technique. The identification of the proteins was performed by Liquid Chromatograph coupled to Mass Spectrometry. Human blood serum altered the characteristics of the nanoparticle, making it less polydisperse, larger and with less negative zeta potential, indicating the formation of the protein corona. Forty-nine proteins (which mostly promote opsonization, phagocytosis and endocytosis in cells of the immune system) were identified and characterized: albumin, IgGs, apoliproteins, serpins, complement (C5), kinases, haptoglobin, glycoproteins and transferrin. Nanoparticle characterization and mass spectrometric data of the digested protein corona suggest improved biocompatibility. Moreover, results regarding nanoparticles’ interaction with macrophages suggest that the corona may have profoun implications for in vitro and in vivo extrapolations and will require some consideration in the future.