Nonmonotonic Superparamagnetic Behavior of the Ferritin Iron Core Revealed via Quantum Spin Relaxometry

Abstract

Ferritin is the primary storage protein in our body and is of significant interest in biochemistry, nanotechnology, and condensed matter physics. More specifically within this sphere of interest are the magnetic properties of the iron core of ferritin, which have been utilized as a contrast agent in applications such as magnetic resonance imaging. This magnetism depends on both the number of iron atoms present, L, and the nature of the magnetic ordering of their electron spins. In this work, we create a series of ferritin samples containing homogeneous iron loads and apply diamond-based quantum spin relaxometry to systematically study their room temperature magnetic properties. We observe anomalous magnetic behavior that can be explained using a theoretical model detailing a morphological change to the iron core occurring at relatively low iron loads. This model provides an L 0.35±0.06 scaling of the uncompensated Fe spins, in agreement with previous theoretical predictions. The necessary inclusion of this morphological change within the model is also supported by electron microscopy studies of ferritin with low iron content. This provides evidence for a magnetic consequence of this morphological change and positions diamond-based quantum spin relaxometry as an effective, noninvasive tool for probing the magnetic properties of metalloproteins. The low detection limit (ferritin 2% loaded at a concentration of 7.5 ± 0.4 μg/mL) also makes this a promising method for precision applications where low analyte concentrations are unavoidable, such as in biological research or even clinical analysis.

In-depth magnetometry and EPR analysis of the spin structure of human-liver ferritin: from DC to 9 GHz

“…[7][8][9] In the past decades, 'bulk' magnetometry techniques have been used to characterize the magnetic and mineral state of ferritin, 10,11 along with spectroscopy techniques such as Mo ¨ssbauer spectroscopy, 11,12 electron paramagnetic resonance (EPR), 13,14 nuclear magnetic resonance (NMR), [15][16][17] as well as electron and X-ray microscopy techniques, 18,19 and diamondbased quantum spin relaxometry to study the ferritin room temperature magnetic properties. 20 Electron paramagnetic resonance (EPR), sometimes also referred to by the more general term electron magnetic resonance (EMR), has also been applied to ferritin, 13,14,[21][22][23][24][25] in spite of intrinsic challenges related to extreme spectral broadening.…”

Minimizing Contact Resistance and Flicker Noise in Micro Graphene Hall Sensors Using Persistent Carbene Modified Gold Electrodes

“…The development of scalable μGHS with reduced contact resistance and flicker noise marks a significant advancement in the field of biomagnetic sensing. Ferritin, an iron-storage protein (∼474 kDa) comprising of a protein shell and a superparamagnetic ferrite core, ,, emerges as a promising biomarker for early diagnosis of HHC in a label-free and minimally invasive setting. − In our work, we employed dispersions of PEG-coated superparamagnetic nanoparticles (SNPs) with an average diameter of 10 nm to mimic ferritin (Figure b). This approach allowed us to readily evaluate the biomagnetic sensing performance of μGHS.…”

A Review of the Current State of Magnetic Force Microscopy to Unravel the Magnetic Properties of Nanomaterials Applied in Biological Systems and Future Directions for Quantum Technologies

“…By this immobilization, the holoferritin molecules can detect changes in B with high precision. Recently, an increase in T 1 magnetic relaxation times with the iron content inside the protein was reported [ 218 ]. This observation is due to the abrupt change in the uncompensated number of spins when the iron is accumulated inside the ferritin core.…”