ABSTRACT
Iron(III)-polymaltose pharmaceutical ferritin analogue Ferrifol® was investigated by high resolution transmission electron microscopy (HRTEM), X-ray diffraction, thermogravimetry, electron magnetic resonance (EMR) spectroscopy, direct current magnetization measurements and 57Fe Mössbauer spectroscopy to get novel information about the structural arrangement of the iron core. The Ferrifol® Mössbauer spectra measured in the range from 295â¯K to 90â¯K demonstrated non-Lorentzian two-peak pattern. These spectra were better fitted using a superposition of 5 quadrupole doublets with the same line width. The obtained Mössbauer parameters were different and an unusual line broadening with temperature decrease was observed. Measurements of the Ferrifol® Mössbauer spectra from 60â¯K to 20â¯K demonstrated a slow decrease of magnetic relaxation in the iron core. Zero-field-cooled and field-cooled magnetization measurements revealed a blocking temperature at ~33â¯K and a paramagnetic state of the Ferrifol® iron core at higher temperatures. Isothermal magnetization measurements at 5â¯K show that the saturation magnetic moment is ~0.31â¯emu/g. X-band EMR spectroscopy measurements revealed the presence of different magnetic species in the sample. Transmission electron microscopy demonstrated that the size of the iron cores in Ferrifol® is in the range 2-6â¯nm. The lattice periodicity in these iron cores, measured on the HRTEM images, vary in the range 2.2-2.7â¯Å. This can be best understood as sets of close packed O(OH) layers in ferrihydrite cores without long range correlation.
