Chemical speciation of iron deposits in thalassemic heart tissue

Abstract

Heart tissue from β-thalassemia/hemoglobin E patients was taken at autopsy. The patients had received no blood transfusions or iron chelation therapy. Ferritin and hemosiderin were isolated from the tissue and studied using 57Fe Mössbauer spectroscopy, transmission electron microscopy and electron diffraction. The ferritin was shown to contain mineral cores with a mean particle size of 7.37 (s.d. 0.84) nm. Electron diffraction and Mössbauer spectroscopy indicated that the cores had structures based on that of the mineral ferrihydrite and were superparamagnetic with a mean blocking temperature of 34 K on the Mössbauer measurement time scale. The hemosiderin particles ranged in size from 1 to 10 nm and were indicated to have a very poor crystalline structure. Mössbauer spectroscopic measurement indicated that the majority of the iron in the hemosiderin was paramagnetic/superparamagnetic at 4.2 K. Mössbauer spectroscopy of the heart tissue indicted that approximately 40% of the tissue iron is in the form of hemosiderin, 35% in the form of ferritin, 3% in the form of heme iron, and approximately 20% in the form of an unidentified form of iron that yields a spectral singlet with centre shift of 0.32 mm s−1 at 15 K with respect to α-iron at room temperature.