Magnetic Nanoparticles in Human Cervical Skin

Abstract

Magnetic iron oxide nanoparticles, magnetite/maghemite, have been identified in human tissues, including the brain, meninges, heart, liver, and spleen. As these nanoparticles may play a role in the pathogenesis of neurodegenerative diseases, a pilot study explored the occurrence of these particles in the cervical (neck) skin of 10 patients with Parkinson's disease and 10 healthy controls. Magnetometry and transmission electron microscopy analyses revealed magnetite/maghemite nanoparticles in the skin samples of every study participant. Regarding magnetite/maghemite concentrations of the single-domain particles, no significant between-group difference was emerged. In low-temperature magnetic measurement, a magnetic anomaly at ~50 K was evident mainly in the dermal samples of the Parkinson group. This anomaly was larger than the effect related to the magnetic ordering of molecular oxygen. The temperature range of the anomaly, and the size-range of magnetite/maghemite, both refute the idea of magnetic ordering of any iron phase other than magnetite. We propose that the explanation for the finding is interaction between clusters of superparamagnetic and single-domain-sized nanoparticles. The source and significance of these particles remains speculative.

Effects of Alzheimer’s disease and formalin fixation on the different mineralised-iron forms in the human brain

“…These higher-than-expected coercivity values could be explained by the presence of elongated particles, which would result in a higher shape anisotropy. However, this hypothesis is not supported by TEM www.nature.com/scientificreports/ analysis of magnetic material extracted from brain tissue, and in-situ imaging 3,13 . An alternative explanation could be the presence of single-domain particles that are magnetically interacting, as suggested by previous experiments on brain 22 and dermal material 3 , which reported a Wohlfarth's ratio < 0.5.…”

Effects of Alzheimer’s disease and formalin fixation on the different mineralised-iron forms in the human brain

“…These higher-than-expected coercivity values could be explained by the presence of elongated particles, which would result in a higher shape anisotropy. However, this hypothesis is not supported by TEM analysis of magnetic material extracted from brain tissue, and in-situ imaging 3,13 . An alternative explanation could be the presence of single-domain particles that are magnetically interacting, as suggested by previous experiments on brain 22 and dermal material 3 , which reported a Wohlfarth's ratio < 0.5.…”

“…Moreover, magnetometry requires minimal sample preparation, contrary to TEM, thus lowering the risk of sample contamination. The observation that IRM curves obtained from human material saturate at magnetic fields of 300 mT or lower, and at temperatures between 50 K and 293 K 2,3,13,17,19,20 , and the occasional observation of the Verwey transition 3,19 , support the use of magnetometry techniques to detect and potentially quantify magnetite and/or oxidised magnetite, i.e. maghemite, nanoparticles in post-mortem or ex-vivo human samples.…”

“…Mineralized iron in the form of magnetite was first detected in the human brain almost thirty years ago 1 . Since then, magnetite has been detected in multiple organs, including the heart 2 , the liver 2 and, most recently, the cervical skin 3 . These findings are of biological interest because magnetite, an iron-oxide mineral hosting both Fe(III) and Fe(II) in its crystal structure, has been proposed as a source of cellular toxicity, involving many different mechanisms.…”

“…While the most compelling evidence for the presence of magnetite in the human material has come from High Resolution Transmission Electron Microscopy (HRTEM) 1 and X-ray techniques 16 , magnetic analyses of Isothermal Remanent Magnetization (IRM) are often employed as complementary tools, or as a means of reporting concentrations of magnetite nanoparticles in the tissue 2,3,13,[17][18][19] . Although these latter measurements require very sensitive magnetometers, they offer the ability to study tissue blocks larger than those that can be studied by TEM, and the dimensions of such blocks are comparable to the spatial resolution of in vivo imaging techniques such as magnetic resonance imaging (MRI), meaning that magnetometry can potentially be employed to guide the interpretation of the contrast of, for example, magnetic susceptibility-weighted MRI images.…”