DECIPHERING THE ORIGIN OF MAGNETITE IN HUMAN BRAIN TISSUE

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Animals from several phyla are thought to detect the magnetic field and use it to their advantage. The most compelling example comes from magnetotactic bacteria that contain single domain (ca. 40-200 nm) magnetite (Fe3O4) or greigite (Fe3S4) crystals, called magnetosomes. Magnetosomes are fixed within the cell that compel the bacteria to swim along magnetic field lines. Interestingly, human brain tissue contains magnetite crystals that have identical morphologies as those found in some magnetotactic bacteria. Our previous work showed a systematic distribution of single domain magnetite in seven dissected, entire post mortem human brains suggesting the body internally biomineralizes the iron oxide. Other studies have reported much smaller (< 40 nm, superparamagnetic) magnetite in human brain tissue and suggested the superparamagnetic magnetite originates from external sources. This proposal aims to determine the properties, concentrations and the origin of both single domain and superparamagnetic magnetite particles in the human brain. We wish to further test whether a difference exists in magnetic characteristics between formalin-fixed tissue and fresh-frozen tissue. We propose to apply unique magnetic methods that will map the relative grain size and chemical composition of the magnetite as well as determine the spatial orientation (anisotropy) of the magnetite crystals in human brains. Systematic distribution in magnetite grain size, magnetite chemistry and/or geometric construction (anisotropy) would constitute groundbreaking evidence to determine the origin of magnetite in the human brain. If the magnetite is indeed shown to have a biogenic origin, then understanding its function in subsequent research should lead to important advances in human brain studies. If environmental, then understanding how the particles enter and become stored in the brain and their reactivity in physiological conditions will likewise have a huge impact on future research.