Preparation, characterization and cytotoxicity of well-dispersed Fe ₃O₄ nanoparticles in aqueous solution and their potential as contrast agents

Well-dispersed Fe₃O₄ nanoparticles were synthesized using Fe(II) and Fe(III) salt chemical coprecipitation with tetramethylammonium hydroxide (N(CH₃)₄OH) in an aqueous solution. TEM, X-ray diffraction (XRD), FT-IR, X-ray photoelectron spectrometer (XPS) and superconducting quantum interference measurement device (SQUID) measurements were employed to investigate the iron oxide properties. The resulting iron oxide particles were manipulated as small as 6 nm diameter in size. Based on FT-IR and X-ray photoelectron spectrometer results, it is suggested that the surfaces of the magnetite (Fe₃O₄) particles are covered with hydroxide (-OH) groups incorporated with (CH₃)₄N ⁺ through electrostatic interaction. The cytotoxicity test revealed that the magnetite particles exhibited in vitro biocompatibility with mouse fibroblasts, suggesting that they can be further explored for biomedical applications. NMR measurements revealed significantly reducing water proton relaxation times T₁ and T₂. The MR image of the nanoparticles in water and serum was investigated. Significant reduction of the background medium signal was achieved in the T2-weigted and the T2*-weighted sequence especially in the serum. Combined the advantage of MRI signal contrast, the versatile surface chemistry for bioconjugation and the homogenous nanometer size for better controlled biodistribution, these preliminary experiments demonstrated the potential of the as-synthesized magnetite material in functional molecular imaging for biomedical research and clinical diagnosis.