Magnetic nanoparticle-based biomolecule imaging with a scanning magnetic particle spectrometer

Abstract

This study reports on a wash-free, inexpensive and sensitive approach of biomolecule imaging with magnetic nanoparticles (MNPs) via a custom-built scanning magnetic particle spectrometer (SMPS). Streptavidin-coated MNPs are used as magnetic biomarkers for the detection of Immunoglobulin G (IgG) conjugated with biotin (IgG-Biotin) while five samples with differentconcentration IgG-Biotin are prepared for experiments. The measurements of the ac susceptibility indicate that the conjugation of the IgG-Biotin onto the surface of the MNPs forms cross-linking between the MNPs, thus increasing the characteristic Brownian relaxation time from 0.627 to 1.448 ms. The ratio of the 3rd to the 1st harmonics is measured on the samples with different-concentration IgG-Biotin in ac magnetic fields with a frequency ranging from about 300 Hz to 2 kHz. It shows that the measurement sensitivity of the IgG-Biotin concentration decreases from 4.62×10 -3 to 0.39×10 -3 nM −1 with increasing excitation frequency. Phantom images of the harmonic ratio, measured with the SMPS, indicate that unbound and bound MNPs can be easily distinguished. Furthermore, the excitation frequency dependence of the contrast-to-noise ratio of the images is discussed based on the measurement sensitivity and the standard deviation of the measured image intensity. This study demonstrates the feasibility of the SMPS for imaging biomolecules bound onto the MNPs, which is of great interest to disease diagnostics and therapy.

Toward Rapid and Sensitive Detection of SARS-CoV-2 with Functionalized Magnetic Nanoparticles

“…To precisely determine the peak frequency despite the limited number of data points, χ″ were fitted with a generalized Debye model with a bimodal lognormal size distribution. 25 The solid lines in Figure 2a,b show that the generalized Debye model fits the experimental data very well. Then, τ B was calculated via the peak frequency f peak of the maximum in the fitted χ″ applying τ B = 1/(2 × π × f peak ).…”

“…This indicates an increase in the effective Brownian relaxation time τ B . 25 For unfunctionalized MNPs, the χ″ shape, shown in Figure 2b, slightly shifts to lower frequencies with increasing c mv . It may be caused by nonspecific binding between the mimic virus and the unfunctionalized MNPs, as well as an increase in the solution viscosity due to the presence of the mimic virus.…”

“…It employs the change in the magnetization dynamics and consequent magnetic response of the MNPs exposed to time-varying magnetic fields [15]. The binding behavior of the biomolecules to functionalized MNPs, dominated by Brownian relaxation, increases their hydrodynamic size or forms cross-linking structures, which significantly changes the Brownian relaxation time of the MNPs and their dynamic magnetization in timevarying magnetic fields [16][17][18]. For instance, for MNPs bound with biomolecules, the harmonics in magnetic particle spectroscopy (MPS) dominated by Brownian relaxation decrease when exposed to a sufficiently strong ac magnetic field.…”

“…35 Zhong et al investigated the effect of binding behavior on the relaxation time of the streptavidincoated MNPs and harmonic ratio for the detection and imaging of biotinylated IgG using streptavidin functionalized MNPs. 25 Yang et al demonstrated the feasibility of wash-free, sensitive, and specific assays for the detection of different viruses, e.g., orchid and influenza viruses, with antibodyfunctionalized MNPs by measuring the reduction in the ACS in mixed-frequency ac magnetic fields. 36 In 2016, Tian et al investigated the detection of Zika virus oligonucleotide via measuring the ACS of functionalized MNPs.…”

Adaptive Model for Magnetic Particle Mapping Using Magnetoelectric Sensors

“…MNPs can be imaged in a variety of ways. MNP imaging techniques that use MNP as tracer material include Magnetic Particle Imaging (MPI) [ 8 , 9 , 10 ], Scanning Magnetic Particle Spectrometry (SMPS) [ 11 , 12 , 13 , 14 ], Magnetorelaxometry Imaging (MRXI) [ 15 , 16 , 17 , 18 ] and Magneto Acoustic Tomography (MAT) [ 19 , 20 , 21 ]. Another type of MNP imaging technique can be categorized into Magnetic Susceptibility Imaging (MSI) [ 22 ], one of which is called Susceptibility Magnitude Imaging (SMI) [ 23 ].…”