arXiv subjects

Diqing Su

Publications and source records attributed to Diqing Su.

15 recordsLinked to original sources

arXiv2020

An Investigation of Commercial Iron Oxide Nanoparticles: Advanced Structural and Magnetic Properties Characterization

Magnetic nanoparticles (MNPs) have been extensively used as tiny heating sources in magnetic hyperthermia therapy, contrast agents in magnetic resonance imaging (MRI), tracers in magnetic particle imaging (MPI), carriers for drug/gene delivery, etc. There have emerged many magnetic nanoparticle/microbeads suppliers since the last decade, such as Ocean NanoTech, Nanoprobes, US Research Nanomaterials, Miltenyi Biotec, micromod Partikeltechnologie GmbH, and nanoComposix, etc. In this paper, we report the physical and magnetic characterizations on iron oxide nanoparticle products from Ocean NanoTech. Standard characterization tools such as Vibrating-Sample Magnetometer (VSM), X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), and Zeta Potential Analyzer are used to provide magnetic nanoparticle customers and researchers with an overview of these iron oxide nanoparticle products. In addition, the dynamic magnetic responses of these iron oxide nanoparticles in aqueous solutions are investigated under low and high frequency alternating magnetic fields, giving a standardized operating procedure for characterizing the MNPs from Ocean NanoTech, thereby yielding the best of magnetic nanoparticles for different applications.

physics.app-ph↗

arXiv2020

Portable Magnetic Particle Spectrometer (MPS) for Future Rapid and Wash-free Bioassays

Nowadays, there is an increasing demand for more accessible routine diagnostics for patients with respect to high accuracy, ease of use, and low cost. However, the quantitative and high accuracy bioassays in large hospitals and laboratories usually require trained technicians and equipment that is both bulky and expensive. In addition, the multi-step bioassays and long turnaround time could severely affect the disease surveillance and control especially in pandemics such as influenza and COVID-19. In view of this, a portable, quantitative bioassay device will be valuable in regions with scarce medical resources and help relieve burden on local healthcare systems. Herein, we introduce the MagiCoil diagnostic device, an inexpensive, portable, quantitative and rapid bioassay platform based on magnetic particle spectrometer (MPS) technique. MPS detects the dynamic magnetic responses of magnetic nanoparticles (MNPs) and uses the harmonics from oscillating MNPs as metrics for sensitive and quantitative bioassays. This device does not require trained technicians to operate and employs a fully automatic, one-step, wash-free assay with user friendly smartphone interface. Using a streptavidin-biotin binding system as a model, we show that the detection limit of the current portable device for streptavidin is 64 nM (equal to 5.12 pmole). In addition, this MPS technique is very versatile and allows for the detection of different diseases just by changing the surface modifications on MNPs.

physics.med-ph↗

arXiv2020

Magnetic Immunoassays: A Review of Virus and Pathogen Detection Before and Amidst the Coronavirus Disease-19 (COVID-19)

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), is a threat to the global healthcare system and economic security. As of July 2020, no specific drugs or vaccines are yet available for COVID-19, fast and accurate diagnosis for SARS-CoV-2 is essential in slowing down the spread of COVID-19 and for efficient implementation of control and containment strategies. Magnetic immunoassay is a novel and emerging topic representing the frontiers of current biosensing and magnetics areas. The past decade has seen rapid growth in applying magnetic tools for biological and biomedical applications. Recent advances in magnetic materials and nanotechnologies have transformed current diagnostic methods to nanoscale and pushed the detection limit to early stage disease diagnosis. Herein, this review covers the literatures of magnetic immunoassay platforms for virus and pathogen detections, before COVID-19. We reviewed the popular magnetic immunoassay platforms including magnetoresistance (MR) sensors, magnetic particle spectroscopy (MPS), and nuclear magnetic resonance (NMR). Magnetic Point-of-Care (POC) diagnostic kits are also reviewed aiming at developing plug-and-play diagnostics to manage the SARS-CoV-2 outbreak as well as preventing future epidemics. In addition, other platforms that use magnetic materials as auxiliary tools for enhanced pathogen and virus detections are also covered. The goal of this review is to inform the researchers of diagnostic and surveillance platforms for SARS-CoV-2 and their performances.

physics.med-ph↗

arXiv2020

Magnetic Particle Spectroscopy: A Short Review of Applications

Magnetic particle spectroscopy (MPS), also called magnetization response spectroscopy, is a novel measurement tool derived from magnetic particle imaging (MPI). It can be interpreted as a zero-dimensional version of MPI scanner. MPS was primarily designed for characterizing superparamagnetic iron oxide nanoparticles (SPIONs) regarding their applicability for MPI. In recent years, it has evolved into an independent, versatile, highly sensitive, inexpensive platform for biological and biomedical assays, cell labeling and tracking, and blood analysis. MPS has also developed into an auxiliary tool for magnetic imaging and hyperthermia by providing high spatial and temporal mappings of temperature and viscosity. Furthermore, other MPS-based applications are being explored such as magnetic fingerprints for product tracking and identification in supply chains. There are a variety of novel MPS-based applications being reported and demonstrated by many groups. In this short review, we highlighted some of the representative applications based on MPS platform, thereby providing a roadmap of this technology and our insights for researchers in this area.

physics.app-ph↗

arXiv2020

Single-core Or Multi-core? A Mini Review on Magnetic Nanoparticles for Magnetic Particle Spectroscopy-based Bioassays

Magnetic particle spectroscopy (MPS) is a technology that derives from magnetic particle imaging (MPI) and thrives as a standalone platform for many biological and biomedical applications, benefiting from the facile preparation and chemical modification of magnetic nanoparticles (MNPs). In recent years, MPS has been reported in extensive literatures as a versatile platform for different bioassay purposes using artificially designed MNPs, where the MNPs serve as magnetic tracers, the surface functionalized reagents (e.g., antibodies, aptamers, peptides, etc.) and tiny probes capturing target analytes from biofluid samples. The biochemical complexes on MNP surfaces can be tailored for different bioassay requirements, while the design of MNPs are of less attention for MPS-based bioassays. For MNPs in most bioassay applications, superparamagnetism is prerequisite to avoid agglomerates and false magnetic signals. Single- and multi-core superparamagnetic nanoparticles (SPMNPs) are prevalently used in MPS-based bioassays. In this mini review, we compared the pros & cons of different MPS platforms realizing volumetric- and surface-based bioassays with single- and multi-core nanoparticles, respectively.

physics.app-ph↗

arXiv2019

Irregularly Shaped γ'-Fe4N Nanoparticles for Hyperthermia Treatment and T2 Contrast-Enhanced Magnetic Resonance Imaging with Minimum Dose

Magnetic nanoparticles (MNPs) have been extensively used in drug/gene delivery, hyperthermia therapy, magnetic particle imaging (MPI), magnetic resonance imaging (MRI), magnetic bioassays, etc. With proper surface chemical modifications, physicochemically stable and non-toxic MNPs are emerging contrast agents and tracers for in vivo MRI and MPI applications. Herein, we report the high magnetic moment, irregularly shaped γ'-Fe4N nanoparticles for enhanced hyperthermia therapy and T2 contrast agent for MRI application. The static and dynamic magnetic properties of γ'-Fe4N nanoparticles are characterized by vibrating sample magnetometer (VSM) and magnetic particle spectroscopy (MPS) systems, respectively. Compared to the γ-Fe2O3 nanoparticles, γ'-Fe4N show at least 3 times higher saturation magnetization (in emu/g), which, as a result, gives rise to the stronger dynamic magnetic responses as proved in the MPS measurement results. In addition, γ'-Fe4N nanoparticles are functionalized with oleic acid layer by a wet mechanical milling process, the morphologies of as-milled nanoparticles are characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and nanoparticle tracking analyzer (NTA). We report that with proper surface chemical modification and tuning on morphologies, γ'-Fe4N nanoparticles could be used as tiny heating sources for hyperthermia and contrast agents for MRI applications with minimum dose.

physics.app-ph↗

arXiv2019

Detection of magnetic nanoparticles (MNPs) using spin current nano-oscillator (SCNO) biosensor: A frequency-based rapid, ultra-sensitive, magnetic bioassay

This Letter is a micromagnetic simulation-based study on the GHz-frequency ferromagnetic resonances for the detection of magnetic nanoparticles (MNPs) using spin current nano-oscillator (SCNO) operating in precession mode as a spintronic biosensor. The magnetic stray fields from the MNPs in an antibody-antigen-MNP complex on the SCNO surface modify the ferromagnetic resonance peaks and generate measurable resonance peak shifts. Moreover, our results strongly indicate the position-sensitive behavior of the SCNO biosensor and ways to eradicate this effect to facilitate better bio-sensing performance. Additionally, a study has been made on how nanoparticles with different sizes can alter the SCNO device performance. This simulation-based study on the SCNO device shows a promise of frequency-based nano-biosensor with a sensitivity of detecting even a single MNP, even in presence of thermal noise.

physics.app-ph↗

arXiv2019

Magnetic Nanoparticle Relaxation Dynamics-based Magnetic Particle Spectroscopy (MPS) for Rapid and Wash-free Molecular Sensing

Magnetic nanoparticles (MNPs) have been extensively used as contrasts and tracers for bioimaging, heating sources for tumor therapy, carriers for controlled drug delivery, and labels for magnetic immunoassays. Here, we describe a MNP relaxation dynamics-based magnetic particle spectroscopy (MPS) method for the quantitative detection of molecular biomarkers. In MPS measurements, the harmonics of oscillating MNPs are recorded and used as a metric for the freedom of rotational motion, which indicates the bound states of the MNPs. These harmonics can be collected from microgram quantities of iron oxide nanoparticles within 10 seconds. Using a streptavidin-biotin binding system, we demonstrate the feasibility of using MPS to sense these molecular interactions, showing this method is able to achieve rapid, wash-free bioassays, and is suitable for future point-of-care (POC), sensitive, and versatile diagnosis.

physics.app-ph↗

arXiv2019

Detection of Influenza A Virus Nucleoprotein Through the Self-Assembly of Nanoparticles in Magnetic Particle Spectroscopy-Based Bioassays: A Method for Rapid, Sensitive, and Wash-free Magnetic Immunoassays

Magnetic nanoparticles (MNPs) with proper surface functionalization have been extensively applied as labels for magnetic immunoassays, carriers for controlled drug/gene delivery, tracers and contrasts for magnetic imaging, etc. Here, we introduce a new biosensing scheme based on magnetic particle spectroscopy (MPS) and the self-assembly of MNPs to quantitatively detect H1N1 nucleoprotein molecules. MPS monitors the harmonics of oscillating MNPs as a metric for the freedom of rotational motion, thus indicating the bound states of MNPs. These harmonics can be readily collected from nanogram quantities of iron oxide nanoparticles within 10 s. H1N1 nucleoprotein molecule hosts multiple different epitopes that forms binding sites for many IgG polyclonal antibodies. Anchoring IgG polyclonal antibodies onto MNPs triggers the cross-linking between MNPs and H1N1 nucleoprotein molecules, thereby forming MNP self-assemblies. Using MPS and the self-assembly of MNPs, we achieved the sensitivity of 44 nM (442 pmole) for detecting H1N1 nucleoprotein. In addition, the morphologies and the hydrodynamic sizes of the MNP self-assemblies are characterized to verify the MPS results. Different MNP self-assembly models such as classical cluster, open ring tetramer, chain model as well as multimers (from dimer to pentamer) are proposed in this paper. Herein, we claim the feasibility of using MPS and the self-assembly of MNPs as a new biosensing scheme for detecting ultralow concentrations of target biomolecules, which can be employed as rapid, sensitive, and wash-free magnetic immunoassays.

physics.app-ph↗

arXiv2019

Tunable Magnetic Domain Walls for Therapeutic Neuromodulation at Cellular Level: Stimulating Neurons Through Magnetic Nanowires

Cellular-level neuron stimulation has attracted much attention in the areas of prevention, diagnosis and treatment of neurological disorders. Herein, we propose a spintronic neurostimulator based on the domain wall movement inside stationary magnetic nanowires driven by the spin transfer torque. The electromotive forces generated by the domain wall motion can serve as highly localized stimulation signals for neuron cells. Our simulation results show that the induced electric field from the domain wall motion in permalloy nanowires can reach up to 14 V/m, which is well above the reported threshold stimulation signal for clinical applications. The proposed device operates on a current range of several uA which is 10^3 times lower compared to magnetic stimulation by microcoils. The duration and amplitude of the stimulating signal can be controlled by adjusting the applied current density, the geometry of the nanowire, and the magnetic properties of the nanowire material.

physics.med-ph↗

arXiv2019

Deterministic Field-free Switching of a Perpendicularly Magnetized Ferromagnetic Layer via the Joint Effects of Dzyaloshinskii-Moriya Interaction and Field-like Spin-orbit Torque: An Appraisal

Field-free switching of perpendicularly magnetized ferromagnetic layer by spin orbit torque (SOT) from the spin Hall effect (SHE) is of great interest in the applications of magnetic memory devices. In this paper, we investigate the deterministic SOT switching through the joint effects of Dzyaloshinskii-Moriya Interaction (DMI) and field-like torque (FLT) by micromagnetic simulations. We confirmed that within a certain range of DMI values and charge current densities, it is possible to deterministically switch the magnetization without the assistance external magnetic field. We show that the FLT could play an adverse role in blocking and slowing down the magnetization switching under certain cases of DMI and charge current-driven field-free switching. However, in other cases, FLT can assist DMI on the deterministic field-free SOT switching. In addition, it is found that FLT can effectively expand the current density window for a deterministic field-free SOT switching in the presence of DMI.

physics.app-ph↗

arXiv2019

Spin-orbit Torque and Spin Hall Effect-based Cellular Level Therapeutic Neuromodulators: Modulating Neuron Activities through Spintronic Nanodevices

Artificial modulation of a neuronal subset through ion channels activation can initiate firing patterns of an entire neural circuit in vivo. As nanovalves in the cell membrane, voltage-gated ion channels can be artificially controlled by the electric field gradient that caused by externally applied time varying magnetic fields. Herein, we theoretically investigate the feasibility of modulating neural activities by using magnetic spintronic nanostructures. An antiferromagnet/ferromagnet (AFM/FM) structure is explored as neuromodulator. For FM layer with perpendicular magnetization, stable bidirectional magnetization switching can be achieved by applying in-plane currents through AFM layer to induce the spin-orbit torque (SOT) due to the spin Hall effect (SHE). This Spin-orbit Torque Neurostimulator (SOTNS) utilizes in-plane charge current pulses to switch the magnetization in FM layer. The time changing magnetic stray field induces electric field that modulates the surrounding neurons. The Object Oriented Micromagnetic Framework (OOMMF) is used to calculate space and time dependent magnetic dynamics of SOTNS structure. The current driven magnetization dynamics in SOTNS has no mechanically moving parts. Furthermore, the size of SOTNS can be down to tens of nanometers, thus, arrays of SOTNSs could be fabricated, integrated together and patterned on a flexible substrate, which gives us much more flexible control of the neuromodulation with cellular resolution.

physics.app-ph↗

arXiv2019

Investigating the Effect of Magnetic Dipole-Dipole Interaction on Magnetic Particle Spectroscopy (MPS): Implications for Magnetic Nanoparticle-based Bioassays and Magnetic Particle Imaging (MPI)

Superparamagnetic iron oxide nanoparticles (SPIONs), with comparable size to biomolecules (such as proteins, nucleic acids, etc.) and unique magnetic properties, good biocompatibility, low toxicity, potent catalytic behavior, are promising candidates for many biomedical applications. There is one property present in most SPION systems, yet it has not been fully exploited, which is the dipole-dipole interaction (also called dipolar interaction) between the SPIONs. It is known that the magnetic dynamics of an ensemble of SPIONs are substantially influenced by the dipolar interactions. However, the exact way it affects the performance of magnetic particle-based bioassays and magnetic particle imaging (MPI) is still an open question. The purpose of this paper is to give a partial answer to this question. This is accomplished by numerical simulations on the dipolar interactions between two nearby SPIONs and experimental measurements on an ensemble of SPIONs using our lab-based magnetic particle spectroscopy (MPS) system. Our results show that even moderate changes in the SPION concentration may have substantial effects on the magnetic dynamics of the SPION system and the harmonic signal magnitudes can be increased or decreased by 60%, depending on the values of MPS system parameters.

physics.app-ph↗

arXiv2019

Tunable Magnetic Skyrmions in Ultrathin Magnetic Nanostructures for Cellular-Level Neurostimulation

In 2016, the Global Burden of Disease reported that neurological disorders were the principal cause of disability-adjusted life years (DALYs) and the second leading cause of deaths. Research in the last decade has pushed neuroscience to design and implement low-cost, efficient, implantable, flexible electrodes/probes and 3D arrays for neuron stimulation and sensing. Electrical arrays used in current CMOS-based technologies can be affected by the migration of cells (such as astrocytes) that attempt to seal off the electronic devices, causing increased impedance and alternations in the electric field. In this regard, magnetic nanodevices can be better candidates. A wide assortment of magnetic skyrmion-based device ideas and models have as of late been proposed featuring their potential applications. In this paper we propose a highly tunable skyrmion-based spintronic nanodevice for neuron stimulation. The effects of tunable material and magnetic properties specifically Dzyaloshinskii-Moriya interaction (DMI), perpendicular magnetic anisotropy (PMA) constant, number of skyrmions and device dimensions on stable skyrmion nucleation and smooth skyrmion dynamics in a magnetic ultra-thin film have been extensively studied. The aim of this study was to meet the standard therapeutic specifications of neuron stimulation, which is an electric field of about 10 mV/mm for a duration of 50 μs. From Faraday's Laws of Induction, skyrmion dynamics that generates an alternating magnetic flux density induces an electric field for a certain time duration in the ultra-thin film. The results of this work show that on tuning the skyrmion dynamics, the induced electric field can reach the standard value required for neurostimulation, thereby providing a strong futuristic possibility to exploit skyrmion-based spintronic nanodevices for neuron stimulation.

physics.app-ph↗

arXiv2018

Magnetic Nanoparticles in Nanomedicine

Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from the bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticle (MNP) is one important class of nanomaterials that have been widely studied for their potential applications in nanomedicine. Due to the fact that MNPs can be detected and manipulated by remote magnetic fields, it opens a wide opportunity for them to be used in vivo. Nowadays, MNPs have been used for diverse applications including magnetic biosensing (diagnostics), magnetic imaging, magnetic separation, drug and gene delivery, and hyperthermia therapy, etc. This review aims to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications of MNPs. In addition, the development of high magnetic moment MNPs with proper surface functionalization has progressed exponentially over the past decade. Herein, we also reviewed the recent advances in the synthesis and surface coating strategies of MNPs. This review is not only to provide in-depth insights into the different synthesis, biofunctionalization, biosensing, imaging, and therapy methods but also to give an overview of limitations and possibilities of each technology.

physics.app-ph↗