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(A) Brownian relaxation: the entire particle including its magnetic moment m physically rotates in the fluid. (B) Néel relaxation: magnetic moment rotates within stational particle core. White arrows represent the magnetization directions in the MNPs. Black arrows represent the rotational directions.
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Since its first report in 2006, magnetic particle spectroscopy (MPS)-based biosensors have flourished over the past decade. Currently, MPS are used for a wide range of applications, such as disease diagnosis, foodborne pathogen detection, etc. In this work, different MPS platforms, such as dual-frequency and mono-frequency driving field designs, we...
Contexts in source publication
Context 1
... will be a reorientation of the magnetic moments of the MNPs subjected to externally applied magnetic fields. As shown in Figure 2, the physical rotation of the MNP's magnetic moment along with its hydrodynamic shell is called the Brownian rotation ( Figure 2A) and the internal rotation of the magnetic moment inside the stational MNP is called Néel relaxation ( Figure 2B). These two distinct physical processes are responsible for the effective relaxation behavior that we observe. ...
Context 2
... will be a reorientation of the magnetic moments of the MNPs subjected to externally applied magnetic fields. As shown in Figure 2, the physical rotation of the MNP's magnetic moment along with its hydrodynamic shell is called the Brownian rotation ( Figure 2A) and the internal rotation of the magnetic moment inside the stational MNP is called Néel relaxation ( Figure 2B). These two distinct physical processes are responsible for the effective relaxation behavior that we observe. ...
Context 3
... will be a reorientation of the magnetic moments of the MNPs subjected to externally applied magnetic fields. As shown in Figure 2, the physical rotation of the MNP's magnetic moment along with its hydrodynamic shell is called the Brownian rotation ( Figure 2A) and the internal rotation of the magnetic moment inside the stational MNP is called Néel relaxation ( Figure 2B). These two distinct physical processes are responsible for the effective relaxation behavior that we observe. ...
Context 4
... number of MNPs captured on the substrate is related to the number of target analytes present in the testing sample, and the higher harmonics' amplitudes are proportional to the remaining MNPs. Figure 4(B2) shows the MPS spectra before and after the capture of MNPs in the presence of target analytes. The biological matrix does not produce any significant harmonic signals since biological tissues and fluids are nonmagnetic or paramagnetic. ...
Citations
... The detection of MNPs can be achieved by using different methods such as susceptometry, relaxometry, and frequency mixing magnetic detection (FMMD) [15,16]. Among these techniques, FMMD, with its portable magnetic reader, has been widely used as a selective technique for detecting and quantifying superparamagnetic nanoparticles (MNPs). ...
Due to the limitations of conventional Brucella detection methods, including safety concerns, long incubation times, and limited specificity, the development of a rapid, selective, and accurate technique for the early detection of Brucella in livestock animals is crucial to prevent the spread of the associated disease. In the present study, we introduce a magnetic nanoparticle marker-based biosensor using frequency mixing magnetic detection for point-of-care testing and quantification of Brucella DNA. Superparamagnetic nanoparticles were used as magnetically measured markers to selectively detect the target DNA hybridized with its complementary capture probes immobilized on a porous polyethylene filter. Experimental conditions like density and length of the probes, hybridization time and temperature, and magnetic binding specificity, sensitivity, and detection limit were investigated and optimized. Our sensor demonstrated a relatively fast detection time of approximately 10 min, with a detection limit of 55 copies (0.09 fM) when tested using DNA amplified from Brucella genetic material. In addition, the detection specificity was examined using gDNA from Brucella and other zoonotic bacteria that may coexist in the same niche, confirming the method’s selectivity for Brucella DNA. Our proposed biosensor has the potential to be used for the early detection of Brucella bacteria in the field and can contribute to disease control measures.
... Target biomolecules increase the hydrodynamic size of the MNPs resulting in increased Brownian relaxation time and change in the signal strength. In the surface-based MPS, the MNPs are bound to the target biomolecules on a reaction surface and are based on the Neel relaxation process [57]. Superparamagnetic iron oxide MNPs and Brownian relaxation-dominated MNPs (BNF-80) are the most widely utilized MNPs in MPS-based biosensors [58][59][60]. ...
Magnetic nanomaterials have emerged as versatile platforms that offer unique advantages in various biomedical applications. With the incorporation of magnetic nanomaterials, which include zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) variants, the field of biosensors is rapidly expanding. This review examines the properties, role, and functionalization of 0D, 1D, and 2D magnetic nanomaterials and highlights their distinct advantages in improving the selectivity, limit of detection (LOD), and specificity in biosensing applications. This article also emphasizes magnetic properties and magnetism-based approaches utilized in the arena of magnetic nanomaterials-based biosensors. In addition, the review covers the recent advances and developments in the integration of magnetic nanomaterials (0D, 1D, and 2D) with various electrochemical, optical, and magnetic-based biosensing techniques for the detection of various biomolecules, pathogens, and diagnosis of numerous diseases.
... Magnetic immunoassays using MNPs have emerged as a promising diagnostic tool for point-of-care testing. This innovative approach utilizes MNPs coated with specific detecting antibodies that selectively capture biological targets, such as viruses, bacteria, and proteins, through antigen-antibody reactions [Cao 2020, Yari 2023, Wu 2019. To maximize the potential of MNPs in bioassays, understanding and tailoring their magnetic behavior is crucial. ...
This letter presents an innovative method for rapid and precise measurement of bacteria in liquid samples for point-of-care testing. The method utilizes the bacteria concentration-dependent ac susceptibility of magnetic nanoparticles, allowing for efficient and practical bacterial detection. The ac susceptibility of the magnetic nanoparticles/bacteria aggregate exhibits a decrease proportional to the bacteria concentration, attributed to the influence of bacteria on the magnetic coupling between the magnetic nanoparticles and magnetic dynamic response of the aggregate. To validate the performance of our method, we conducted measurements on Fusobacterium nucleatum samples obtained from both healthy individuals and cancer patients. The results demonstrated a robust correlation (correlation factor up to 0.94) between our measurements and the results obtained through quantitative polymerase chain reaction (qPCR) analysis, highlighting the high precision and accuracy of our method in quantifying bacteria, which is comparable to a qPCR system. The simplified apparatus not only reduces costs but also saves time by eliminating the need for DNA amplification of short segments, making it a promising alternative for rapid and precise bacterial measurement in point-of-care testing.
... In recent years, there has been a significant increase in the development of biosensing platforms that aim to achieve rapid and reliable detection of various diseases, pathogens, and environmental factors [25][26][27][28][29]. These platforms offer an alternative to conventional methods that are often expensive, time-consuming and require specialized equipment and personnel. ...
In this paper, we introduce a novel design of a metamaterial unit cell absorber, which is based on a metal/insulator/metal sandwich structure. The design is subjected to comprehensive finite element method (FEM) computational analysis to ensure accurate and reliable results. The proposed metamaterial sandwich structure demonstrates exceptional absorption performance, achieving a nearly perfect absorption rate of 99.996% at the resonance infrared frequency of 39.8 THz. To provide a detailed theoretical explanation of nearly perfect absorption, we employ the effective medium theory, impedance matching, and field distribution analysis. Additionally, we have optimized the structural parameters of the sensor to maximize its absorption peak. This includes optimizing the thickness of the gold (Au) layer (from 0.03 to 0.28 μm), the distance between the L shape corners (from 0.60 to 0.90 μm), and the thickness of SiC dielectric spacer (from 0.20 to 0.45 μm). Furthermore, we showcase the remarkable sensitivity of the proposed metamaterial unit cell in detecting subtle changes in the refractive index through the implementation of a sensing medium setup in our model. Remarkably, we achieve a frequency shift sensitivity of 3.74 THz/RIU, along with a quality factor (Q-factor) of 10.33, for a wide range of refractive indices (1.0 - 2.0). Moreover, for cancer detection, we attain a sensitivity of 3.5 THz/RIU. These findings highlight the exceptional performance of our approach in accurately detecting changes in refractive index, making it a promising candidate for various sensing applications. The novelty of our work lies in the design of a metamaterial unit cell structure. This configuration exhibits several noteworthy features, including wide incident angle (θ) coverage up to 60o, polarization insensitivity, exceptional frequency shift sensitivity, high absorption peaks across a wide range of refractive indices, and the ability to distinguish cancer cells from healthy ones.
... In such cases, non-equilibrium states exist at each instantaneous time. These dynamic, non-equilibrium magnetization responses of MNPs play a crucial role in many applications involving high frequency AC magnetic fields, such as magnetic hyperthermia , magnetic particle imaging (MPI) [21,22,[50][51][52][53], magnetic resonance imaging (MRI) [54][55][56][57][58], and magnetic particle spectroscopy (MPS) [59][60][61][62][63]. Thus, in section 4, we review mathematical models that predict the dynamic, non-equilibrium magnetization responses of MNPs. ...
Nowadays, magnetic nanoparticles (MNPs) have been extensively used in biomedical fields such as labels for magnetic biosensors, contrast agents in magnetic imaging, carriers for drug/gene delivery, and heating sources for hyperthermia, among others. They are also utilized in various industries, including data and energy storage and heterogeneous catalysis. Each application exploits one or more physicochemical properties of MNPs, including magnetic moments, magnetophoretic forces, nonlinear dynamic magnetic responses, magnetic hysteresis loops, and others. It is generally accepted that the static and dynamic magnetizations of MNPs can vary due to factors such as material composition, crystal structure, defects, size, shape of the MNP, as well as external conditions like the applied magnetic fields, temperature, carrier fluid, and inter-particle interactions (i.e., MNP concentrations). A subtle change in any of these factors leads to different magnetization responses. In order to optimize the MNP design and external conditions for the best performance in different applications, researchers have been striving to model the macroscopic properties of individual MNPs and MNP ensembles. In this review, we summarize several popular mathematical models that have been used to describe, explain, and predict the static and dynamic magnetization responses of MNPs. These models encompass both individual MNPs and MNP ensembles and include the Stoner-Wohlfarth model, Langevin model, zero/non-zero field Brownian and Néel relaxation models, Debye model, empirical Brownian and Néel relaxation models under AC fields, the Landau–Lifshitz–Gilbert (LLG) equation, and the stochastic Langevin equation for coupled Brownian and Néel relaxations, as well as the Fokker–Planck equations for coupled/decoupled Brownian and Néel relaxations. In addition, we provide our peers with the advantages, disadvantages, as well as suitable conditions for each model introduced in this review.
Most of the sensors currently used for wind turbine generator system (WTGS) oil detection can only perform measurements of a single physical quantity, and some sensors are capable of measuring multiple contaminants but require switching modes to achieve this, making it impossible to detect various oil contaminants simultaneously. These methods not only require the addition of numerous sensors and burden the WTGS piping but also increase the time and cost of maintenance and inspection. In addition, it may be unable to respond quickly to specific emergencies. To address these limitations, this study proposes an LC-based passive dual solenoid coil multicontaminant oil detection sensor. An analytical expression for the magnetic field strength of the dual solenoidal coil is derived, and a corresponding mathematical model is developed. The validity of the model is verified compared it with the finite element analysis results. An experimental verification was carried out. The experimental results show that the sensor can recognize multiple oil pollutants simultaneously according to different signal curves without switching modes. The sensor can detect iron particles with diameters larger than
$38 \mu \text{m}$
, copper particles with diameters larger than
$100 \mu \text{m}$
, liquid droplets with diameters larger than 100–
$110 \mu \text{m}$
, and air bubbles with diameters larger than 180–
$190 \mu \text{m}$
. By comparing with the existing sensors, the LC-based passive dual-coil multipollutant oil detection sensor proposed in this article has a broad application prospect in real-time monitoring of wind turbine oil conditions.
p>Magnetic particle imaging (MPI) is a tracer imaging modality that detects superparamagnetic iron oxide nanoparticles (SPIOs), enabling sensitive, radiation-free imaging of cells and disease pathologies. The arbitrary waveform relaxometer (AWR) is an indispensable platform for developing magnetic nanoparticle tracers and evaluating tracer performance for magnetic particle imaging applications. One of the biggest challenges in arbitrary waveform excitation is direct feedthrough interference, which is usually six orders of magnitude larger than the signal from magnetic nanoparticles. This work will showcase hardware that suppresses this interference by an order of magnitude, increasing the dynamic range of the instrument and enabling mass-limited detection at full scale range. </p
p>Magnetic particle imaging (MPI) is a tracer imaging modality that detects superparamagnetic iron oxide nanoparticles (SPIOs), enabling sensitive, radiation-free imaging of cells and disease pathologies. The arbitrary waveform relaxometer (AWR) is an indispensable platform for developing magnetic nanoparticle tracers and evaluating tracer performance for magnetic particle imaging applications. One of the biggest challenges in arbitrary waveform excitation is direct feedthrough interference, which is usually six orders of magnitude larger than the signal from magnetic nanoparticles. This work will showcase hardware that suppresses this interference by an order of magnitude, increasing the dynamic range of the instrument and enabling mass-limited detection at full scale range. </p
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.
