Magnetic nanoparticles colourization by a mixing-frequency method
TL;DR: In this paper, the mixing-frequency method was used to identify different MNPs simultaneously, where a low-frequency sinusoidal magnetic field is applied to saturate the MNPs periodically.
Abstract: Brownian and Neel relaxation of magnetic nanoparticles (MNPs) can be characterized by a highly sensitive mixing-frequency method using a search-coil based detection system. The unique magnetic properties of MNPs have been used for biomarkers detection. In this paper, we present a theory and implement an experimental detection scheme using the mixing-frequency method to identify different MNPs simultaneously. A low-frequency sinusoidal magnetic field is applied to saturate the MNPs periodically. A high-frequency sinusoidal magnetic field is then applied to generate mixing-frequency signals that are highly specific to the magnetization of MNPs. The spectra of each MNP can be defined as the complex magnetization of the MNPs over the field frequency. The magnetic spectra of various MNPs and magnetic beads have been characterized and compared. The differences between the MNPs spectra enable us to identify the individual MNPs at the same time. A test has been done to verify the ratio of two different MNPs in mixed samples based on the proposed theory. The experimental results show that the mixing-frequency method is a promising method for MNPs colourization.
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TL;DR: A comprehensive assessment of the state-of-the-art biological and biomedical applications of magnetic nanoparticles can be found in this paper, where the authors provide in-depth insights into the different synthesis, biofunctionalization, biosensing, imaging, and therapy methods.
Abstract: Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticles (MNPs) are 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. Specifically, we reviewed some emerging techniques in magnetic diagnostics such as magnetoresistive (MR) and micro-Hall (μHall) biosensors, as well as the magnetic particle spectroscopy, magnetic relaxation switching and surface enhanced Raman spectroscopy (SERS)-based bioassays. Recent advances in applying MNPs as contrast agents in magnetic resonance imaging and as tracer materials in magnetic particle imaging are reviewed. In addition, the development of high magnetic moment MNPs with proper surface functionalization has progressed exponentially over the past decade. To this end, different MNP synthesis approaches and surface coating strategies are reviewed and the biocompatibility and toxicity of surface functionalized MNP nanocomposites are also discussed. Herein, we are aiming to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications 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.
268 citations
TL;DR: Different MNP synthesis approaches and surface coating strategies are reviewed and the biocompatibility and toxicity of surface functionalized MNP nanocomposites are discussed, aiming to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications of MNPs.
Abstract: 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.
248 citations
61 citations
05 May 2020
TL;DR: Magnetic particle spectroscopy (MPS) also called magnetization response spectroscope (MRS) is a versatile measurement tool derived from magnetic particle imaging (MPI) as discussed by the authors.
Abstract: Magnetic particle spectroscopy (MPS), also called magnetization response spectroscopy (MRS), is a versatile measurement tool derived from magnetic particle imaging (MPI). It can be interpreted as a...
55 citations
TL;DR: In this article, a MNP Brownian relaxation dynamics-based magnetic particle spectroscopy (MPS) method for the quantitative detection of molecular biomarkers is described. But the method is not suitable for very low-concentration biomarker detection scenarios, as the harmonics of oscillating MNPs are largely dependent on the quantity of the MNPs in the sample.
Abstract: 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 Brownian 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 s. As the harmonics are largely dependent on the quantity of the MNPs in the sample, the MPS bioassay results could be biased by the deviations of MNP quantities in each sample, especially for the very low-concentration biomarker detection scenarios. Herein, we report three MNP concentration/quantity-independent metrics for characterizing the bound states of MNPs in MPS. Using a streptavidin-biotin binding system as a model, we demonstrate the feasibility of using MPS and MNP concentration/quantity-independent metrics to sense these molecular interactions, showing that this method can achieve rapid, wash-free bioassays, and is suitable for future point-of-care, sensitive, and versatile diagnosis.
39 citations
References
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TL;DR: In this paper, the authors developed analytical relationships and computations of power dissipation in magnetic fluid (ferrofluid) subjected to alternating magnetic field and showed that the dissipation results from the orientational relaxation of particles having thermal fluctuations in a viscous medium.
2,111 citations
TL;DR: In this paper, a biomagnetic sensor scheme based on Brownian relaxation of magnetic nanoparticles suspended in liquids is presented, and the characteristic time scale of the relaxation can be determined directly by ac susceptibility measurements as a function of frequency.
Abstract: We experimentally demonstrate a biomagnetic sensor scheme based on Brownian relaxation of magnetic nanoparticles suspended in liquids. The characteristic time scale of the Brownian relaxation can be determined directly by ac susceptibility measurements as a function of frequency. The peak in the imaginary part of the ac susceptibility shifts to lower frequencies upon binding the target molecules to the magnetic nanoparticles. The frequency shift is consistent with an increase of the hydrodynamic radius corresponding to the size of the target molecule.
228 citations
TL;DR: In this paper, a new type of biosensor was developed based on detection of nanosized superparamagnetic particles that serve as labels in bioreactions, which is based on non-linear magnetic material detection by a magnetic field having components at two frequencies f 1 and f 2.
185 citations
TL;DR: It is observed that MNPs 15 nm in diameter generate maximum signal amplitude in MPI experiments at 250 kHz, and the authors expect the physical basis for this result, the change in magnetic relaxation with MNP size, will impact MPI under other experimental conditions.
Abstract: Purpose:
Magnetic particle imaging (MPI), using magnetite nanoparticles (MNPs) as tracer material, shows great promise as a platform for fast tomographic imaging. To date, the magnetic properties of MNPs used in imaging have not been optimized. As nanoparticle magnetism shows strong size dependence, the authors explore how varying MNP size impacts imaging performance in order to determine optimal MNP characteristics for MPI at any driving field frequencyf0.
Methods:
Monodisperse MNPs of varying size were synthesized and their magnetic properties characterized. Their MPI response was measured experimentally using a custom-built MPI transceiver designed to detect the third harmonic of MNP magnetization. The driving field amplitudeH0=6 mT μ0−1 and frequency f0=250 kHz were chosen to be suitable for imaging small animals. Experimental results were interpreted using a model of dynamic MNP magnetization that is based on the Langevin theory of superparamagnetism and accounts for sample size distribution and size-dependent magnetic relaxation.
Results:
The experimental results show a clear variation in the MPI signal intensity as a function of MNP diameter that is in agreement with simulated results. A maximum in the plot of MPI signal vs MNP size indicates there is a particular size that is optimal for the chosenf0.
Conclusions:
The authors observed that MNPs 15 nm in diameter generate maximum signal amplitude in MPI experiments at 250 kHz. The authors expect the physical basis for this result, the change in magnetic relaxation with MNP size, will impact MPI under other experimental conditions.
156 citations
TL;DR: In this article, a novel magnetic reader for quantification of magnetic particle concentrations has been developed for magnetic immunoassay applications, and the optimization of field coils, differential pickup coil, preamplifier, demodulators and filters are discussed.
155 citations