Quantification of absolute iron content in mineral cores of cytosolic ferritin molecules in human liver

The authors present aberration corrected scanning transmission electron microscopy (SuperSTEM) and electron energy loss spectroscopy (EELS) spectrum imaging data for the iron hydroxide mineral cores of cytosolic ferritin molecules in situ within human liver sections measured at a controlled electron dose. The authors have quantified the absolute iron content in individual cores using EELS and have checked the results against similar data obtained from synthetic maghemite nanoparticles of known composition and dimensions. Using these results the authors have then determined the quantitative relationship between the STEM high angle annular dark field (HAADF) image intensity of a ferritin core normalised to the background matrix intensity and the absolute iron content of the core as determined by EELS. This procedure then allows us to perform a rapid assessment of the iron content of any core within a tissue section based on the STEM HAADF image intensity.