Characterizing Physical Properties of Superparamagnetic Nanoparticles in Liquid Phase Using Brownian Relaxation

Abstract

Superparamagnetic iron oxide nanoparticles (SPIONs) have been extensively used as bioimaging contrast agents, heating sources for tumor therapy, and carriers for controlled drug delivery and release to target organs and tissues. These applications require elaborate tuning of the physical and magnetic properties of the SPIONs. The authors present here a search-coil-based method to characterize these properties. The nonlinear magnetic response of SPIONs to alternating current magnetic fields induces harmonic signals that contain information of these nanoparticles. By analyzing the phase lag and harmonic ratios in the SPIONs, the authors can predict the saturation magnetization, the average hydrodynamic size, the dominating relaxation processes of SPIONs, and the distinction between single- and multicore particles. The numerical simulations reveal that the harmonic ratios are inversely proportional to saturation magnetizations and core diameters of SPIONs, and that the phase lag is dependent on the hydrodynamic volumes of SPIONs, which corroborate the experimental results. Herein, the authors stress the feasibility of using search coils as a method to characterize physical and magnetic properties of SPIONs, which may be applied as building blocks in nanoparticle characterization devices.

Detection of Influenza a Virus in Swine Nasal Swab Samples With a Wash-Free Magnetic Bioassay and a Handheld Giant Magnetoresistance Sensing System

“…The magnetic tags were streptavidin-coated superparamagnetic microbeads with an average hydrodynamic volume of 50 nm (Gaster et al, 2011; Wang et al, 2014; Wu et al, 2017b) (2 × 10 12 particles/mL; Catalog No. 130-048-101, Miltenyi Biotec, Inc., Auburn, CA, USA), referred to as MACS in this paper.…”

“…130-048-101, Miltenyi Biotec, Inc., Auburn, CA, USA), referred to as MACS in this paper. Each MACS microbead consists of smaller nanoparticles (α-Fe 2 O 3 and Fe 3 O 4 with an average size of ~8 nm) embedded in a matrix of dextran (Wu et al, 2017b). The superparamagnetic nature of these nanoparticles effectively avoids the aggregation and precipitation of MACS microbeads in solution.…”

Magnetic Particle Spectroscopy: A Short Review of Applications Using Magnetic Nanoparticles

“…15,21,40,41 Furthermore, other MPS-based applications that are sometimes overlooked but owns great market potentials such as the characterization of SPIONs from aqueous medium, the marking/tracking of products in the complex global resource and supply chains, the determination of total blood volume and the evaluation of blood clot progression. 15,16,[42][43][44][45][46] In this short review, we are only able to list some of the representative applications and the MPS-based applications are not limited to this paper. We hope this review could provide insights into the great potential of MPS and serve as a roadmap for researchers in this area.…”

Tracking the Growth of Superparamagnetic Nanoparticles with an In-Situ Magnetic Particle Spectrometer (INSPECT)

“…On the other hand, there has been an immense progress in the development of MPS devices as, for instance, one-dimensional MPS without offset and with various excitation frequencies, two-dimensional Lissajous MPS, arbitrary-waveform spectrometer and many more 21–23 , developed for different MPI associated applications. Moreover, there are also new approaches to characterize the SPIONs such as a frequency-mixing method based on search coils, which measure the phase lag of the magnetic moment compared to the drive field, giving more precise information regarding saturation magnetization and average hydrodynamic size 24 . The measurements from MPS devices usually consist of amplitude and phase spectra.…”