Magnetite Fe₃O₄ Has no Intrinsic Peroxidase Activity, and Is Probably not Involved in Alzheimer's Oxidative Stress

Abstract

Despite stated in some highly cited articles, magnetite is devoided of peroxidase activity. In fact, this very stable mixed valence Fe O⋅Fe O complex is not catalytically competent to oxidize standard peroxidase substrates, especially at the biologically relevant pH value of 7.4. In addition, magnetite whose deleterious redox activity has been suspected in Alzheimer's disease brain damages, does not significantly interact with amyloid peptide Aβ in vitro, and is not able to induce, either in the presence or absence of Aβ, the reductive activation of dioxygen, the first step of an oxidative stress. In fact, this highly insoluble mineral iron derivative is probably not involved in the oxidative damage of brain neurons of patients with AD.

Single‐Atom Nanozyme Based on Nanoengineered Fe–N–C Catalyst with Superior Peroxidase‐Like Activity for Ultrasensitive Bioassays

“…In the first experiment, possible adventitious iron impurities in the acetate buffer (pH 3.5) was removed though overnight Chelex-100 treatment. [21,35] The absorbance at 652 nm of single-atom dispersed CNT/FeNC in non Chelex-100 treatment buffer was 1.280 after 5 min (Figure 2b, black), while it went down to 0.910 in Chelex-100 treatment buffer (Figure 2b, red).…”

“…Under the optimized condition, the catalytic capacity parameter (turnover number, TON) and catalytic kinetic parameter (Michaelis constant, K m ) were calculated, respectively. In order to compare with classical Fe 3 O 4 nanozyme, [21] TON was defined as the number of moles of the TMB generated per catalyst mole during 5 min of the reaction. According to Lambert-Beer law (ε TMB = 39,000 M -1 cm -1 ), single-atom dispersed CNT/FeNC nanozyme produced △ Abs/(ε TMB *l) = 0.91/(39,000*l) = 0.23×10 -4 M of TMB product.…”

“…[3,12] However, the catalytic activities of the peroxidase-like nanozyme are still much inferior to natural peroxidases like HRP. [21] This weakness significantly affects its potential applications.…”

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

“…Therefore, being able to determine the magnetic properties of iron nanoparticles, their concentration in the brain, their source, i.e. whether they are of biogenic or of anthropogenic origin 13 , and their reactivity in physiological conditions 14,15 may reveal important information on Alzheimer's disease and possibly other neurodegenerative diseases that are accompanied by brain iron accumulation 4 .…”

Significant Upregulation of Alzheimer's β‐Amyloid Levels in a Living System Induced by Extracellular Elastin Polypeptides

“…The etiology of AD is complex and the mechanistic elucidation of AD pathogenesis remains inconclusive. It has been challenging to comprehensively determine pathological events contributing to the onset and progression of AD . Presently, there is an urgent need to identify and investigate new factors that may trigger Aβ overproduction in the neuronal microenvironment and to further unravel the pathogenesis of AD.…”