In recent decades, considerable efforts have been made to understand the mechanism of memory, cognition, and relevant
neurodegenerative diseases in the human brain. Several studies have shown the importance of
microtubule proteins in the memory mechanism and memory dysfunction. Microtubules possess dynamicity, which is essential for functions of neuronal networks.
Microtubule-associated proteins, i.e., tau, play vital roles in microtubule stability. On the other hand, the ferromagnetic
mineral magnetite (Fe(3)O(4)) has been detected in the normal human brain, and elevated levels of
magnetite are also observed in the brains of
Alzheimer's disease patients. Therefore, we propose that a relationship between microtubule organization in axons and brain magnetite nanoparticles is possible. In this study we found alterations of microtubule polymerization in the presence of increasing concentrations of
magnetite through transmission electron microscopy images and a turbidimetry method. Structural changes of microtubule and
tau protein, as an essential
microtubule-associated protein for
tubulin assembly, were detected via circular dichroism spectroscopy, intrinsic fluorescence, and
8-anilino-1-naphthalenesulfonic acid fluorometry. We predicted three possible binding sites on
tau protein and one possible binding site on
tubulin dimer for magnetite nanoparticles.
Magnetite also causes the morphology of PC12 cells to change abnormally and cell viability to decrease. Finally, we suggest that
magnetite changes microtubule dynamics and polymerization through two paths: (1) changing the secondary and tertiary structure of
tubulin and (2) binding to either
tubulin dimer or
tau protein and preventing tau-
tubulin interaction.