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Magnetic Contrast Imaging: Magnetic Nanoparticles as Probes in Living Systems
Published in Jeffrey N. Anker, O. Thompson Mefford, Biomedical Applications of Magnetic Particles, 2020
Robert C. Woodward, Matthew R. J. Carroll, Micheal J. House, Timothy G. St Pierre
Developed by Gleich and Weizenecker in 2005 (Gleich and Weizenecker 2005), magnetic particle imaging (MPI) makes use of the non-linear magnetization curve of magnetic nanoparticles to generate images of the particle concentration in a subject. In zero field, the response of a magnetic particle to a small alternating field is large. However, if a significant field is applied, the particle’s magnetization saturates and the response to the alternating field diminishes. The technique uses a series of three field gradients to generate a single point in space with zero field. It then detects the magnetic response as a signal in the receiver coils at the drive frequency of the AC field and its higher harmonics. This signal is dominated by the particles in and around the zero field point. The zero field point is then scanned through space using a 3D Lissajous trajectory.1 The main advantage of MPI is that it can generate 3D images of particle concentrations in real time (Weizenecker et al. 2009). To do this presently requires a calibration of the scanner at the voxel level in order to solve the inverse reconstruction problem. Several issues still need to be overcome prior to successful commercial development, including improving the signal-to-noise ratio, generating high field gradients in a human-sized scanner, and controlling patient heating due to the alternating magnetic field (Weizenecker et al. 2009).
Introduction
Published in Shoogo Ueno, Bioimaging, 2020
Magnetic nanoparticles (MNPs) are used as medical tracers as well as MRI contract agents. MPI is an imaging technique to visualize MNPs for biomedical applications (Gleich and Weizenecker 2005, Weizenecker et al., 2009). MPI allows us to obtain the direct quantitative imaging of the spatial distribution of MNPs with a high spatial and a high temporal resolution. MPI exploits the unique characteristics of MNPs when AC and DC gradient fields are applied. The DC gradient field produces the so-called field-free point (FFP) or field-free line (FFL) where the field becomes zero. The FFP or FFL makes it possible to detect MNPs with a high spatial resolution because the magnetic signal is selectively generated from the MNPs located near the FFP or FFL. Understanding of the dynamic magnetization of MNPs under AC and DC gradient fields is important, as MPI hardware and imaging technology are developed (Yoshida et al., 2013, Enpuku et al., 2017).
Nanomagnetism
Published in Chun Huh, Hugh Daigle, Valentina Prigiobbe, Maša Prodanović, Practical Nanotechnology for Petroleum Engineers, 2019
Chun Huh, Hugh Daigle, Valentina Prigiobbe, Maša Prodanović
Magnetic particle imaging (MPI) is a new tomographic imaging technique which measures the spatial distribution of superparamagnetic nanoparticles (Biederer et al. 2009; Gleich 2014; Gleich and Weizenecker 2005). MPI is a quantitative imaging modality, providing high sensitivity and sub-millimeter spatial resolution. Furthermore, the acquisition time is short, allowing for real time applications.
One-pot synthesis of iron oxide nanoparticles: Effect of stirring rate and reaction time on its physical characteristics
Published in Inorganic and Nano-Metal Chemistry, 2022
Auni Hamimi Idris, Che Azurahanim Che Abdullah, Nor Azah Yusof, Mohd Basyaruddin Abdul Rahman
Iron oxide nanoparticles (IONP) have received considerable attention in the past decade in the biomedical field due to their biocompatibility and magnetic properties. Research is currently being carried out to employ IONP in magnetic resonance imaging (MRI),[1] magnetic particle imaging (MPI),[2] magnetic hyperthermia,[3] and magnetic drug targeting (MDT).[4] Three types of iron oxide commonly used in biomedicine are magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe2O3).[5] The magnetic characteristics of IONP can be tuned based on their size and shape to suit the intended purpose. IONP with a core diameter size less than 20 nm typically exhibits superparamagnetism, i.e., the magnetic moments are only present when exposed to a magnetic field and return to zero when the magnetic field is removed,[6] making them especially suitable for clinical applications.
Advances of engineered extracellular vesicles-based therapeutics strategy
Published in Science and Technology of Advanced Materials, 2022
Hiroaki Komuro, Shakhlo Aminova, Katherine Lauro, Masako Harada
Besides the three current most common methods of in vivo imaging, there are always new types of imaging being created. One such method involves using superparamagnetic iron oxide nanoparticles (SPIONs) in combination with magnetic resonance imaging (MRI) or magnetic particle imaging (MPI) [256,257]. SPIONs are magnetic nanoparticles that are commonly used for imaging cells with MRIs in the blood, perfusion, and metastatic tumors, and have recently transitioned to being used to image EVs. Advantages to using MRI over nuclear imaging include the absence of radiation and low toxicity, thus increasing safety and easing the transition to clinical applications. Additionally, SPIONs do not require genetic modification as they can be applied by incubating donor cells with SPION containing media, washing/replacing media, and collecting supernatant after incubation [227], or by electroporation with isolated EVs [228]. The downsides of using SPIONs include possible false positives, low sensitivity, and lack of accurate quantification, unlike nuclear imaging. This can be seen in Jia et al., who engineered EVs to present RGE, a targeting ligand for glioma, and loaded the EVs with Curcumin as a tumor therapeutic and SPIONs for MRI. The researchers found the labeled EVs targeted and had an inhibitory effect on the tumor, while the SPION allowed for visualization of the tumor, leading to possible diagnosis and evaluation uses [129]. Another alternative is gold nanoparticles (GNPs), which are commonly used in combination with computed tomography (CT) imaging and surface Raman spectroscopy (SERS) [234,255]. An advantage that comes with using GNPs is their high biocompatibility and stability [255,258]. Lara et al. labeled B16F10 derived EVs with GNP, PEG, and folic acid (FA) conjugate to assist with the internalization of GNP while studying the biodistribution of the EVs without changing the EV surface. The GNP labeling allowed for precise localization and quantification of the EVs [234]. SPIONS and GNPs are just a couple of up-and-coming alternative EV imaging tools, and depending on the requirement on the experiment, may be a better fit compared to the usual three tools used currently. Collectively, to visualize the biodistribution of EVs, it is possible to track engineered EVs with various imaging modalities. These modalities using engineered EVs would allow for the creation of novel designated EVs for therapeutic applications.