Alternating current (AC) susceptibility as a particle-focused probe of coating and clustering behaviour in magnetic nanoparticle suspensions

Narayanasamy, K.; Cruz‐Acuña, Melissa; Everett, James; Dobson, Jon; Telling, Neil D.

doi:10.1016/j.jcis.2018.08.014

Cited by 23 publications

(20 citation statements)

References 28 publications

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“…Coating of the particles with polyethyleneimine changes the frequency of the χ peak because of the change of τ B . The peaks associated with Arrhenius behaviour (due to moment reorientation only, see equation 57) were found to be well separated from these Brownian relaxation peaks [56]. By way of contrast, nickel nanoparticles deposited in silica cannot physically re-orientate leading to slow relaxation controlled by magnetic moment reorientation only shown in figure 12 [57].…”

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 94%

“…Superparamagnets and single molecule magnets (SMMs) are arguably the simplest systems exhibiting slow magnetic relaxation. A superparamagnet describes an assembly of magnetic particles, each of which have sufficiently small physical size that domain wall formation is not possible and the magnetization in each particle becomes a single magnetic domain [1,21] These are sometimes referred to as magnetic nanoparticles [55,56,57]. SMMs (sometimes called zero-dimensional molecular magnets) are a subset of the greater class of molecular magnets [1,58].…”

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

“…For quantum tunnelling to occur there must be some additional term in the Hamiltonian that does not commute with S z [1,59]. This is achieved for nonzero E in equation (56) [1,59], though other higherorder terms can also contribute, all depending on the relevant symmetries of the magnetic ions in the molecule [1]. Quantum tunnelling can take place when energy levels on either side of the energy barrier become degenerate and so is more likely at zero applied d.c. magnetic field and at higher fields corresponding to new energy levels being brought into degeneracy [59,64,58].…”

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

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A.C. susceptibility as a probe of low-frequency magnetic dynamics

Topping

Blundell

2018

J. Phys.: Condens. Matter

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The experimental technique of a.c. susceptibility can be used as a probe of magnetic dynamics in a wide variety of systems. Its use is restricted to the lowfrequency regime and thus is sensitive to relatively slow processes. Rather than measuring the dynamics of single spins, a.c. susceptibility can be used to probe the dynamics of collective objects, such as domain walls in ferromagnets or vortex matter in superconductors. In some frustrated systems, such as spin glasses, the complex interactions lead to substantial spectral weight of fluctuations in the low-frequency regime, and thus a.c. susceptibility can play a unique role. We review the theory underlying the technique and magnetic dynamics more generally and give applications of a.c. susceptibility to a wide variety of experimental situations.

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Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 94%

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

Section: Superparamagnets and Single Molecule Magnetsmentioning

confidence: 99%

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A.C. susceptibility as a probe of low-frequency magnetic dynamics

Topping

Blundell

2018

J. Phys.: Condens. Matter

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“…The preparation and characterization of MNP-PEIs used in this study are described in detail elsewhere 28 . Briefly, MNPs were prepared using the thermal decomposition method 4 to obtain largely spherical monodisperse particles with a mean core size of 17.4 nm and 15% polydispersivity.…”

Section: Resultsmentioning

confidence: 99%

“…The MNP-PEIs used were synthesized using thermal decomposition, coated with PEI and characterized as described previously 28 .…”

Section: Cell Culturementioning

confidence: 99%

Effect of PEI-coated MNPs on the Regulation of Cellular Focal Adhesions and Actin Stress Fibres

Narayanasamy

Price

Merkhan

et al. 2019

Preprint

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The biocompatibility of surface coated/functionalised magnetic nanoparticles (MNPs) is key to their successful incorporation and application in biological systems. Polyethylene imine (PEI) -coated MNPs provide improved in vitro transfection efficiency compared to conventional chemical methods such as Lipofectamine and cationic polymers, and are also safer than viral transduction. Commercial cell toxicity assays are useful for end-point and high-throughput screening, providing fast results and an overview of cell health. However these assays only take into account cells that have undergone an extreme toxic response leading to cell death. Cell toxicity is a complex process which can be expressed in many forms, through morphological, metabolic, and epigenetic changes. A common indicator of cell stress and toxic response is increased cell adhesion and stress fibre formation. It is important to identify these changes in cells as it may affect downstream results and applications in biomedicine. This study explores the effect of the nanomagnetic transfection agent PEI-coated MNPs (MNP-PEIs) and an external magnetic field on cell behaviour, by studying particle internalization, changes in cellular morphology, and cell adhesion. We found that MNP-PEIs induced cell stress through a dose-dependent increase in cell adhesion via the overexpression of vinculin and formation of actin stress fibres. While the presence of PEI was the main contributor to increased cell stress, free PEI polyplexes induced higher toxicity compared to PEI bound to MNPs. MNPs without PEI coating however did not adversely affect cells suggesting a chemical effect instead of a mechanical one. In addition, genes identified as being associated with actin fibre regulation and cell adhesion, showed significant increases in expression due to the internalization of the MNP-PEI complex. From these results, we identify anomalous cell behaviour, morphology, and gene expression after interaction with MNP-PEIs, as well as a safe dosage to reduce acute cell toxicity.

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Magnetic Nanoparticles: A Review on Synthesis, Characterization, Functionalization, and Biomedical Applications

Rezaei,

Yari,

Sanders

et al. 2023

Small

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Nowadays, magnetic nanoparticles (MNPs) are applied in numerous fields, especially in biomedical applications. Since biofluidic samples and biological tissues are nonmagnetic, negligible background signals can interfere with the magnetic signals from MNPs in magnetic biosensing and imaging applications. In addition, the MNPs can be remotely controlled by magnetic fields, which make it possible for magnetic separation and targeted drug delivery. Furthermore, due to the unique dynamic magnetizations of MNPs when subjected to alternating magnetic fields, MNPs are also proposed as a key tool in cancer treatment, an example is magnetic hyperthermia therapy. Due to their distinct surface chemistry, good biocompatibility, and inducible magnetic moments, the material and morphological structure design of MNPs has attracted enormous interest from a variety of scientific domains. Herein, a thorough review of the chemical synthesis strategies of MNPs, the methodologies to modify the MNPs surface for better biocompatibility, the physicochemical characterization techniques for MNPs, as well as some representative applications of MNPs in disease diagnosis and treatment are provided. Further portions of the review go into the diagnostic and therapeutic uses of composite MNPs with core/shell structures as well as a deeper analysis of MNP properties to learn about potential biomedical applications.

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Alternating current (AC) susceptibility as a particle-focused probe of coating and clustering behaviour in magnetic nanoparticle suspensions

Cited by 23 publications

References 28 publications

A.C. susceptibility as a probe of low-frequency magnetic dynamics

A.C. susceptibility as a probe of low-frequency magnetic dynamics

Effect of PEI-coated MNPs on the Regulation of Cellular Focal Adhesions and Actin Stress Fibres

Magnetic Nanoparticles: A Review on Synthesis, Characterization, Functionalization, and Biomedical Applications

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