Types Of Magnetic Nanoparticles Research Articles

A Concise Review on Magnetic Nanoparticles: Their Properties, Types, Synthetic Methods, and Current Trending Applications

Abstract: In recent years, there has been significant research on developing magnetic nanoparticles (MNPs) with multifunctional characteristics. This review focuses on the properties and various types of MNPs, methods of their synthesis, and biomedical, clinical, and other applications. These syntheses of MNPs were achieved by various methods, like precipitation, thermal, pyrolysis, vapor deposition, and sonochemical. MNPs are nano-sized materials with diameters ranging from 1 to 100 nm. The MNPs have been used for various applications in biomedical, cancer theranostic, imaging, drug delivery, biosensing, environment, and agriculture. MNPs have been extensively researched for molecular diagnosis, treatment, and therapeutic outcome monitoring in a range of illnesses. They are perfect for biological applications, including cancer therapy, thrombolysis, and molecular imaging, because of their nanoscale size, surface area, and absence of side effects. In particular, MNPs can be used to conjugate chemotherapeutic medicines (or) target ligands/proteins, making them beneficial for drug delivery. However, up until that time, some ongoing issues and developments in MNPs include toxicity and biocompatibility, targeting accuracy, regulation and safety, clinical translation, hyperthermia therapy, immunomodulatory effects, multifunctionality, and nanoparticle aggregation.

An efficient magnetothermal actuation setup for fast heating/cooling cycles or long-term induction heating of different magnetic nanoparticle classes

Alternating magnetic fields (AMFs) in the ∼100 kHz frequency regime cause magnetic nanoparticles (MNPs) to dissipate heat to their nanoscale environment. This mechanism is beneficial for a variety of applications in biomedicine and nanotechnology, such as localized heating of cancer tissue, actuation of drug release, or inducing conformational changes of molecules. However, engineering electromagnetic resonant circuits which generate fields to efficiently heat MNPs over long time scales, remains a challenge. In addition, many applications require fast heating/cooling cycles over ΔT= 5 °C–10 °C to switch the sample between different states. Here, we present a home-built magnetothermal actuation setup maximized in its efficiency to deliver stable AMFs as well as to enable fast heating/cooling cycles of MNP samples. The setup satisfies various demands, such as an elaborate cooling system to control heating of the circuit components as well as of the sample due to inductive losses. Fast cycles of remote sample heating/cooling (up to ±15 °C min−1) as well as long-term induction heating were monitored via contact-free thermal image recording at sub-mm resolution. Next to characterizing the improved hyperthermia setup, we demonstrate its applicability to heat different types of MNPs: ‘nanoflower’-shaped multicore iron oxide nanoparticles, core shell magnetite MNPs, as well as magnetosomes from magnetotactic bacteria (Magnetospirillum gryphiswaldense). MNPs are directly compared in their structure, surface charge, magnetic properties as well as heating response. Our work provides practical guidelines for AMF engineering and the monitoring of MNP heating for biomedical or nano-/biotechnological applications.

Renal clearable magnetic nanoparticles for magnetic resonance imaging and guided therapy.

Magnetic resonance imaging (MRI) is a non-invasive, radiation-free imaging technique widely used for disease detection and therapeutic evaluation due to its infinite penetration depth. Magnetic nanoparticles (MNPs) have unique magnetic and physicochemical properties, making them ideal as contrast agents for MRI. However, the in vivo toxicity of MNPs, resulting from metal ion leakage and long-term accumulation in the reticuloendothelial system (RES), limits their clinical application. To overcome these challenges, there is considerable interest in the development of renal-clearable MNPs that can be completely cleared through the kidney, reducing retention time and potential toxic risks. In this review, we provide an overview of recent advancements in the development of renal-clearable MNPs for disease imaging and treatment. We discuss the factors influencing renal clearance, summarize the types of renal-clearable MNPs, their synthesis methods, and biomedical applications. This review aims to offer comprehensive information for the design and clinical translation of renal-clearable MNPs. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > Biosensing.

A Novel Cell Membrane-Associated RNA Extraction Method and Its Application in the Discovery of Breast Cancer Markers.

Cell membrane-associated RNA (mem-RNA) has been demonstrated to be cell-specific and disease-related and are considered as potential biomarkers for disease diagnostics, drug delivery, and cell screening. However, there is still a lack of methods specifically designed to extract mem-RNA from cells, limiting the discovery and applications of mem-RNA. In this study, we propose the first all-in-one solution for high-purity mem-RNA isolation based on two types of magnetic nanoparticles, named MREMB (Membrane-associated RNA Extraction based on Magnetic Beads), which achieved ten times enrichment of cell membrane components and over 90% recovery rate of RNA extraction. To demonstrate MREMB's potential in clinical research, we extracted and sequenced mem-RNA of typical breast cancer MCF-7, MDA-MB-231, and SKBR-3 cell lines and non-neoplastic breast epithelial cell MCF-10A. Compared to total RNA, sequencing results revealed that membrane/secreted protein-encoding mRNAs and long noncoding RNAs (lncRNAs) were enriched in the mem-RNA, some of which were significantly overexpressed in the three cancer cell lines, including extracellular matrix-related genes COL5A1 and lncRNA TALAM1. The results indicated that MREMB could enrich membrane/secreted protein-coding RNA and amplify the expression differences of related RNAs between cancer and non-neoplastic cells, promising for cancer biomarker discovery.

Field-Swept Magnetic Particle Spectroscopy: A Single-Harmonic Method for Simultaneous Determination of Magnetic Nanoparticle Types and Quantities

Magnetic particle spectroscopy (MPS) allows for highly sensitive and real time characterization of magnetic nanoparticles (MNPs). When combined with surface-modified MNPs that can specifically bind to biomarkers, MPS can serve as a quantitative biosensing platform and have shown enormous potential in point-of-care diagnosis. To improve diagnostic efficiency and accuracy, the simultaneous detection of multiple biomarkers has been studied in MPS, which requires the simultaneous determination of the type and quantity of MNPs. Current methods generally rely on the higher order harmonics (e.g., third to fifth harmonic ratio) of the MNPs’ magnetic responses to the excitation fields, but facing challenges at low concentrations or with small-sized MNPs that are difficult to generate sufficient harmonics. In this paper, we propose a single-harmonic method for simultaneous determination of MNP types and quantities, named field-swept magnetic particle spectroscopy (FS-MPS). An adjustable static magnetic field perpendicular to the alternating magnetic field is introduced and MNPs’ field-dependent response is registered from the static field direction. By comparing simulation results of serval system configurations and the field-swept spectra of different harmonics, we found that the second harmonic component of the MNP signal combines good specificity and robustness with no direct feed-through interference issues. We built the first FS-MPS device and carried out experiments of binary MNP mixtures to verify the effectiveness of the proposed method. Our experimental results showed that the proposed method has up to 90% accuracy for the simultaneous determination of two types of MNPs with a maximum concentration ratio of 9:1. The proposed method can in principle determine more types of MNPs simultaneously, providing an effective tool for the detection of multiple biomolecular markers.

Magnetic Nanoparticle Coating Decreases the Senescence and Increases the Targeting Potential of Fibroblasts and Adipose-Derived Mesenchymal Stem Cells.

Magnetic nanoparticles (MNPs) are intensely scrutinized for applications in emerging biomedical fields. Their potential use for drug delivery, tracking, and targeting agents or for cell handling is tested for regenerative medicine and tissue engineering applications. The large majority of MNPs tested for biomedical use are coated with different lipids and natural or synthetic polymers in order to decrease their degradation process and to increase the ability to transport drugs or bioactive molecules. Our previous studies highlighted the fact that the as-prepared MNP-loaded cells can display increased resistance to culture-induced senescence as well as ability to target pathological tissues; however, this effect tends to be dependent on the cell type. Here, we assessed comparatively the effect of two types of commonly used lipid coatings, oleic acid (OA) and palmitic acid (PA), on normal human dermal fibroblasts and adipose-derived mesenchymal cells with culture-induced senescence and cell motility in vitro. OA and PA coatings improved MNPs stability and dispersibility. We found good viability for cells loaded with all types of MNPs; however, a significant increase was obtained with the as-prepared MNPs and OA-MNPs. The coating decreases iron uptake in both cell types. Fibroblasts (Fb) integrate MNPs at a slower rate compared to adipose-derived mesenchymal stem cells (ADSCs). The as-prepared MNPs induced a significant decrease in beta-galactosidase (B-Gal) activity with a nonsignificant one observed for OA-MNPs and PA-MNPs in ADSCs and Fb. The as-prepared MNPs significantly decrease senescence-associated B-Gal enzymatic activity in ADSCs but not in Fb. Remarkably, a significant increase in cell mobility could be detected in ADSCs loaded with OA-MNPscompared to controls. The OA-MNPs uptake significantly increases ADSCs mobility in a wound healing model in vitro compared to nonloaded counterparts, while these observations need to be validated in vivo. The present findings provide evidence that support applications of OA-MNPs in wound healing and cell therapy involving reparative processes as well as organ and tissue targeting.

In Silico Experiments to Explore the Heating Efficiency of Magnetic Nanoparticles in Hyperthermia Preclinical Tests

AbstractPreclinical tests on murine models are typically performed to evaluate the therapeutic efficacy of novel magnetic nanoparticles (MNPs) in cancer treatment with magnetic hyperthermia. Here, through in silico experiments, in vivo tests are mimicked on a 30 g mouse and a 500 g rat, with the aim of determining the optimal treatment conditions allowing to reach the therapeutic temperature range (40−45 °C) within tumor regions. Various types of MNPs are considered with very different heating properties in terms of specific loss power, varying their administered dose, as well as the frequency and peak amplitude of the magnetic field. The analysis is performed by means of finite element models that solve the low‐frequency electromagnetic (EM) field problem and the Pennes’ bioheat transfer equation, to calculate the temperature increase in biological tissues due to the combined effects of EM field exposure and MNP activation. The methodology, which can be generalized to any type of MNPs, has permitted to identify the proper doses of MNPs to be administered to the tumor region, as a function of their heating properties and magnetic field parameters, highlighting the conditions that can lead to possible overheating, generation of hot spots or magnetic hyperthermia inefficacy.

Relaxation spectral analysis in multi-contrast vascular magnetic particle imaging.

Magnetic nanoparticles (MNPs) are used as tracers without ionizing radiation in vascular imaging, molecular imaging, and neuroimaging. The relaxation mechanisms of magnetization in response to excitation magnetic fields are important features of MNPs. The basic relaxation mechanisms include internal rotation (Néel relaxation) and external physical rotation (Brownian relaxation). Accurate measurement of these relaxation times may provide high sensitivity for predicting MNP types and viscosity-based hydrodynamic states. It is challenging to separately measure the Néel and Brownian relaxation components using sinusoidal excitation in conventional MPI. We developed a multi-exponential relaxation spectral analysis method to separately measure the Néel and Brownian relaxation times in the magnetization recovery process in pulsed vascular MPI. Synomag-D samples with different viscosities were excited using pulsed excitation in a trapezoidal-waveform relaxometer. The samples were excited at different field amplitudes ranging from 0.5 to 10 mT at intervals of 0.5 mT. The inverse Laplace transform-based spectral analysis of the relaxation-induced decay signal in the field-flat phase was performed by using PDCO, a primal-dual interior method for convex objectives. Néel and Brownian relaxation peaks were elucidated and measured on samples with various glycerol and gelatin concentrations. The sensitivity of viscosity prediction of the decoupled relaxation times was evaluated. A digital vascular phantom was designed to mimic a plaque with viscous MNPs and a catheter with immobilized MNPs. Spectral imaging of the digital vascular phantom was simulated by combining a field-free point with homogeneous pulsed excitation. The relationship between the Brownian relaxation time from different tissues and the number of periods for signal averages was evaluated for a scan time estimation in the simulation. The relaxation spectra of synomag-D samples with different viscosity levels exhibited two relaxation time peaks. The Brownian relaxation time had a positive linear relationship with the viscosity in the range 0.9 to 3.2 mPa · s. When the viscosity was >3.2 mPa · s, the Brownian relaxation time saturated and did not change with increasing viscosity. The Néel relaxation time decreased slightly with an increase in the viscosity. The Néel relaxation time exhibited a similar saturation effect when the viscosity level was >3.2 mPa · s for all field amplitudes. The sensitivity of the Brownian relaxation time increased with the field amplitude and was maximized at approximately 4.5 mT. The plaque and catheter regions were differentiated from the vessel region in the simulated Brownian relaxation time map. The simulation results show that the Néel relaxation time was 8.33±0.09 μs in the plaque region, 8.30±0.08 μs in the catheter region, and 8.46±0.11 μs in the vessel region. The Brownian relaxation time was 36.60±2.31 μs in the plaque region, 30.17±1.24 μs in the catheter region, and 31.21±1.53 μs in the vessel region. If we used 20 excitation periods for image acquisition in the simulation, the total scan time of the digital phantom was approximately 100 s. Quantitative assessment of the Néel and Brownian relaxation times through inverse Laplace transform-based spectral analysis in pulsed excitation, highlighting their potential for use in multi-contrast vascular MPI.

A method for multiplexed and volumetric-based magnetic particle spectroscopy bioassay: mathematical study

Magnetic particle spectroscopy (MPS) is an emerging biosensing technique that detects target analytes by exploiting the dynamic magnetic responses of magnetic nanoparticles (MNPs). Due to the ease of synthesis and surface chemical functionalization of MNPs, MPS-based bioassays have gained popularity around the globe. One limiting factor for MPS-based assay is the ability to detect multiple analytes simultaneously in a single run, namely, multiplexed bioassay. Several groups have reported the realization of multiplexed bioassays on surface-based MPS platforms by spatially separating reaction areas by using the unique magnetic responses of different MNPs. In this work, we systematically study the magnetization curves (M-H curves) of different types of MNPs and their relationship to the dynamic magnetic responses when subjected to AC magnetic driving fields. Due to the different structures, sizes, and magnetic properties of each kind of MNP, the resulting harmonics are unique. Thus, concurrent quantification (also called ‘colorization’) of each type of MNP in a mixture is possible by solving the harmonic matrix function. Our results show that the uniqueness of M-H response curves of selected types of MNP and the signal-to-noise ratio of the system can affect the accuracy of multiplexed, volumetric-based MPS bioassays. The reported method assumes that each type of MNPs nanoparticles does not interact, and that the magnetic response of the mixture is a linear combination of the responses of each kind of MNP. This assumption may not hold for very dense systems where inter-particle interactions become significant and may require more complex models.

Size and Composition Control of Magnetic Nanoparticles

Magnetite nanoparticles are a type of magnetic nanoparticle (MNP) that are inexpensive to make and can be formed in different shapes and sizes. MNPs can be used in DNA/RNA purification, drug delivery, and other biomedical applications. The commonly employed solvothermal route to make these MNPs gives the most uniform products with the smallest size distribution, but there is a need to identify easily controlled changes to reaction parameters that can reliably tune the size and composition of the MNPs made by this method. In this work we report simple and reliable methods whereby adjusting the total water content and basic salt concentration affords size and composition control, respectively. We employ synchrotron X-ray absorption measurements to prove our method offers monotonic control over MNP composition from maghemite-rich (γ-Fe2O3) to the more magnetic magnetite (Fe3O4). This demonstrates a simple, general method to produce particles with high magnetite concentration and the desired size.

Experimental Comparison of Methods to Evaluate Heat Generated by Magnetic Nanofluids Exposed to Alternating Magnetic Fields

The paper aims to compare different methods able to estimate the specific loss power (SLP) generated by three different types of magnetic nanoparticles, MNPs, dispersed in a suspension fluid, e.g., octane or water. The nanoparticles were characterized morphologically in terms of shape and size, chemically for composition and their physical properties like magnetization and SLP were studied. We evidenced the differences in SLP evaluation due to the applied method, particularly in the presence of thermally induced phenomena such as aggregation or precipitation of MNPs that can affect the heating curve of the samples. Then, the SLP determination methods less sensible to this phenomenon appear to be the ones that use the initial slope when the sample is in quasi-adiabatic condition. Finally, we propose a comparison of those methods based on the pros and cons of their use for the SLP determination of magnetic nanofluids. In particular, the analysis of the behavior of the heating curve is useful to evaluate the useful amplitude of the interval analysis for the initial slope methods.

Multi-criterion optimization of invasive antenna applicators for Au@Fe3O4, Au@-Fe2O3 and Au@-Fe2O3 mediated microwave ablation treatment

ABSTRACT Magnetic nanoparticle (MNP) mediated microwave ablation has the great potential at present to address challenges associated with treatment planning such as maximum heat generation in the vicinity of targeted tissues in lesser penetration time. Further, the antenna applicators injected in human phantom must be rigid and thin. The derivative-free optimization algorithms are carried out for optimum design of monopole, slot, dipole, and tapered slot antenna applicators for ablation of tumour tissues invasively. It is found that in terms of input impedance matching, the used multi-criterion Nelder-Mead optimization performs efficiently for tapered slot applicator achieving S 11 value of –40 dB with much reduced antenna dimensions. In order to further escalate the performance of tapered slot antenna, gold (Au)-coated iron-based MNPs are suggested for tumor infusion. Spherical gold-coated shell material is preferrable for more sphericity of ablation zone, biocompatibility and due to high conductivity, heat generated in MNPs can be transferred to biological tissues more rapidly. The size, type, and shape of MNPs also influence the heat generation in tumor tissues. Thus, three different types of MNPs having high magnetization properties, Au@Fe3O4, Au@-Fe2O3 and Au@-Fe2O3 have been employed to study the performance in terms of maximum rise in temperature, specific absorption rate (SAR), and area of ablation zone by varying core size radius of MNPs. Results demonstrate that increase in radius of MNP core helps in increasing the temperature distribution and reduction in ablation zone. The optimized lesion is achieved for 20 nm core radius of Au@Fe3O4.

Numerical Study on the Magnetization Characteristics of Chainlike Magnetic Nanoparticles

This work investigated chainlike magnetic nanoparticles (CMNPs), which are a type of magnetic nanoparticle (MNP) with a dipole–dipole interaction in which individual nanoparticles are connected to form a chainlike structure. We numerically analyzed the ac magnetization characteristics of the CMNP and the single-core MNP (SMNP) using the Landau–Lifshitz–Gilbert equation. Owing to the magnetic dipole–dipole interaction, the magnetization of the CMNP is approximately 10 times that of the SMNP under a certain excitation field. MNPs with a chainlike structure are thus expected to have enhanced magnetization characteristics and better performance in medical applications. Additionally, it was found that stronger magnetization can be expected from a CMNP connecting 10 or more magnetic cores with a size of approximately 10–12 nm.

Surfactant-driven optimization of iron-based nanoparticle synthesis: a study on magnetic hyperthermia and endothelial cell uptake.

This work examines the effect of changing the ratio of different surfactants in single-core iron-based nanoparticles with respect to their specific absorption rate in the context of magnetic hyperthermia and cellular uptake by human umbilical vein endothelial cells (HUVEC). Three types of magnetic nanoparticles were synthesized by separately adding oleic acid or oleylamine or a mixture of both (oleic acid/oleylamine) as surfactants. A carefully controlled thermal decomposition synthesis process led to monodispersed nanoparticles with a narrow size distribution. Spherical-shaped nanoparticles were mainly obtained for those synthesized with oleic acid, while the shape changed upon adding oleylamine. The combined use of oleic acid and oleylamine as surfactants in single-core iron-based nanoparticles resulted in a substantial saturation magnetization, reaching up to 140 A m2 kg-1 at room temperature. The interplay between these surfactants played a crucial role in achieving this high magnetic saturation. By modifying the surface of the magnetic nanoparticles using a mixture of two surfactants, the magnetic fluid hyperthermia heating rate was significantly improved compared to using a single surfactant type. This improvement can be attributed to the larger effective anisotropy achieved through the modification with both (oleic acid/oleylamine). The mixture of surfactants enhances the control of interparticle distance and influences the strength of dipolar interactions, ultimately leading to enhanced heating efficiency. Functionalization of the oleic acid-coated nanoparticles with trimethoxysilane results in the formation of a core-shell structure Fe@Fe3O4, showing exchange bias (EB) associated with the exchange anisotropy between the shell and the core. The biomedical relevance of our synthesized Fe@Fe3O4 nanoparticles was demonstrated by their efficient uptake by human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. This remarkable cellular uptake highlights the potential of these nanoparticles in biomedical applications.

Frequency and Amplitude Optimizations for Magnetic Particle Spectroscopy Applications

Nowadays, there is a growing interest in the field of magnetic particle spectroscopy (MPS)-based bioassays. MPS monitors the dynamic magnetic response of surface-functionalized magnetic nanoparticles (MNPs) upon excitation by an alternating magnetic field (AMF) to detect various target analytes. This technology has flourished in the past decade due to its low cost, low background magnetic noise interference from the biomatrix, and fast response time. A large number of MPS variants have been reported by different groups around the world, with applications ranging from disease diagnosis to foodborne pathogen detection and virus detection. However, there is an urgent need for guidance on how to optimize the sensitivity of MPS detection by choosing different types of MNPs, AMF modalities, and MPS assay strategies (i.e., volume- and surface-based assays). In this work, we systematically study the effect of AMF frequencies and amplitudes on the responses of single- and multicore MNPs under two extreme conditions, namely, the bound and unbound states. Our results show that some modalities such as dual-frequency MPS utilizing multicore MNPs are more suitable for surface-based bioassay applications, whereas single-frequency MPS systems using single- or multicore MNPs are better suited for volumetric bioassay applications. Furthermore, the bioassay sensitivities for these modalities can be further improved by a careful selection of AMF frequencies and amplitudes.

Fungus-Based Magnetic Nanobiocomposites for Environmental Remediation

The use of a variety of microorganisms for the degradation of chemicals is a green solution to the problem of environmental pollution. In this work, fungi–magnetic nanoparticles were studied as systems with the potential to be applied in environmental remediation and pest control in agriculture. High food demand puts significant pressure on increasing the use of herbicides, insecticides, fungicides, pesticides, and fertilizers. The global problem of water pollution also demands new remediation solutions. As a sustainable alternative to commercial chemical products, nanobiocomposites were obtained from the interaction between the fungus M. anisopliae and two different types of magnetic nanoparticles. Fourier transform infrared spectroscopy, optical and electron microscopy, and energy dispersive spectroscopy were used to study the interaction between the fungus and nanoparticles, and the morphology of individual components and the final nanobiocomposites. Analyses show that the nanobiocomposites kept the same morphology as that of the fungus in natura. Magnetic measurements attest the magnetic properties of the nanobiocomposites. In summary, these nanobiocomposites possess both fungal and nanoparticle properties, i.e., nanobiocomposites were obtained with magnetic properties that provide a low-cost approach benefiting the environment (nanobiocomposites are retrievable) with more efficiency than that of the application of the fungus in natura.

Biosensors and Drug Delivery in Oncotheranostics Using Inorganic Synthetic and Biogenic Magnetic Nanoparticles.

Magnetic nanocarriers have attracted attention in translational oncology due to their ability to be employed both for tumor diagnostics and therapy. This review summarizes data on applications of synthetic and biogenic magnetic nanoparticles (MNPs) in oncological theranostics and related areas. The basics of both types of MNPs including synthesis approaches, structure, and physicochemical properties are discussed. The properties of synthetic MNPs and biogenic MNPs are compared with regard to their antitumor therapeutic efficiency, diagnostic potential, biocompatibility, and cellular toxicity. The comparative analysis demonstrates that both synthetic and biogenic MNPs could be efficiently used for cancer theranostics, including biosensorics and drug delivery. At the same time, reduced toxicity of biogenic particles was noted, which makes them advantageous for in vivo applications, such as drug delivery, or MRI imaging of tumors. Adaptability to surface modification based on natural biochemical processes is also noted, as well as good compatibility with tumor cells and proliferation in them. Advances in the bionanotechnology field should lead to the implementation of MNPs in clinical trials.

Resolving ambiguities in core size determination of magnetic nanoparticles from magnetic frequency mixing data

Frequency mixing magnetic detection (FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for the characterization and distinction (also known as “colourization”) of different types of magnetic nanoparticles (MNPs) based on their core sizes. In a previous work, it was shown that the large particles contribute most of the FMMD signal. This leads to ambiguities in core size determination from fitting since the contribution of the small-sized particles is almost undetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome by modelling the signal intensity using the Langevin model in thermodynamic equilibrium including a lognormal core size distribution fL(dc,d0,σ) fitted to experimentally measured FMMD data of immobilized MNPs. For each given median diameter d0, an ambiguous amount of best-fitting pairs of parameters distribution width σ and number of particles Np with R2 > 0.99 are extracted. By determining the samples’ total iron mass, mFe, with inductively coupled plasma optical emission spectrometry (ICP-OES), we are then able to identify the one specific best-fitting pair (σ, Np) one uniquely. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, σ, Np) directly from FMMD measurements, allowing precise MNPs sample characterization.

Cover Feature: Magnetic Relaxation and Modification of Thiol Groups on Co‐Mg Ferrite Nanoparticles for Theranostics (ChemNanoMat 10/2022)

Magnetic nanoparticles (MNPs) have been actively researched for biomedical applications. This work reports the magnetic and thermal properties of various types of MNPs and confirms a significant hyperthermia effect of Mn-Zn ferrite nanoparticles in human breast cancer cells. Doping with Co ions with larger anisotropy is a possible approach to obtain higher magnetization. However, Co-ferrite particles exhibit hysteresis in their magnetization curves, hindering the maintenance of the superparamagnetic behavior. In contrast, Mg-ferrite micro-order clusters have remarkable heat generation properties for hyperthermia treatment in external magnetic fields. Thus, new properties can be expected from the synergistic effect of Co and Mg ions. Co1-xMgxFe2O4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) nanoparticles embedded in amorphous SiO2 with particle sizes of approximately 4.5 nm were prepared using an original wet chemical method. Spin-echo magnetic resonance imaging measurements were performed for Co1-xMgxFe2O4 nanoparticles using a 0.3-T MRI system. The particles exhibited a significant T2 shortening effect compared with that of agarose, depending on the composition. All particles exhibited effective relaxivity, R2, and a significant contrast was observed in the phantom image. More information can be found in the Research Article by Yuko Ichiyanagi et al.

From Bench to Cell: A Roadmap for Assessing the Bioorthogonal "Click" Reactivity of Magnetic Nanoparticles for Cell Surface Engineering.

In this work, we report the use of bioorthogonal chemistry, specifically the strain-promoted click azide–alkyne cycloaddition (SPAAC) for the covalent attachment of magnetic nanoparticles (MNPs) on living cell membranes. Four types of MNPs were prepared, functionalized with two different stabilizing/passivation agents (a polyethylene glycol derivative and a glucopyranoside derivative, respectively) and two types of strained alkynes with different reactivities: a cyclooctyne (CO) derivative and a dibenzocyclooctyne (DBCO) derivative. The MNPs were extensively characterized in terms of physicochemical characteristics, colloidal stability, and click reactivity in suspension. Then, the reactivity of the MNPs toward azide-modified surfaces was evaluated as a closer approach to their final application in a living cell scenario. Finally, the DBCO-modified MNPs, showing superior reactivity in suspension and on surfaces, were selected for cell membrane immobilization via the SPAAC reaction on the membranes of cells engineered to express azide artificial reporters. Overall, our work provides useful insights into the appropriate surface engineering of nanoparticles to ensure a high performance in terms of bioorthogonal reactivity for biological applications.