Hydrodynamic and magnetic fractionation of superparamagnetic nanoparticles for magnetic particle imaging

Löwa, Norbert; Knappe, Patrick; Wiekhorst, Frank; Eberbeck, Dietmar; Thünemann, Andreas F.; Trahms, Lutz

doi:10.1016/j.jmmm.2014.08.057

Cited by 19 publications

(19 citation statements)

References 20 publications

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“…The particle harmonic spectrum of a sample is influenced by the behavior of magnetic relaxation, i.e., Néel and Brownian relaxations, which is why SP particles are good in contrast agents. There are numerous studies underway to produce MNP with improved contrast properties for MRI, or tracer material for MPI [ 4 , 7 , 12 , 13 , 14 ]. MPI studies recommend that the MNP should be monodisperse with little anisotropy and a single core, and a particle size around 20–30 nm [ 7 , 15 , 16 ].…”

Section: Introductionmentioning

confidence: 99%

“…MPI studies recommend that the MNP should be monodisperse with little anisotropy and a single core, and a particle size around 20–30 nm [ 7 , 15 , 16 ]. “Gold-standard” Resovist ® has been used as the standard for comparing the MPI signal strength in terms of harmonic spectra [ 14 , 17 , 18 ]. Since Resovist is no longer commercially available, efforts focus presently on synthesizing and testing new materials that will yield similar if not better, image quality.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Methods to Estimate the Efficiency of Magnetic Nanoparticles in Imaging

et al. 2017

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Magnetic resonance imaging (MRI) and magnetic particle imaging (MPI) are powerful methods in the early diagnosis of diseases. Both imaging techniques utilize magnetic nanoparticles that have high magnetic susceptibility, strong saturation magnetization, and no coercivity. FeraSpinTM R and its fractionated products have been studied for their imaging performances; however, a detailed magnetic characterization in their immobilized state is still lacking. This is particularly important for applications in MPI that require fixation of magnetic nanoparticles with the target cells or tissues. We examine the magnetic properties of immobilized FeraSpinTM R, its size fractions, and Resovist®, and use the findings to demonstrate which magnetic properties best predict performance. All samples show some degree of oxidation to hematite, and magnetic interaction between the particles, which impact negatively on image performance of the materials. MRI and MPI performance show a linear dependency on the slope of the magnetization curve, i.e., initial susceptibility, and average blocking temperature. The best performance of particles in immobilized state for MPI is found for particle sizes close to the boundary between superparamagnetic (SP) and magnetically ordered, in which only Néel relaxation is important. Initial susceptibility and bifurcation temperature are the best indicators to predict MRI and MPI performance.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced Methods to Estimate the Efficiency of Magnetic Nanoparticles in Imaging

et al. 2017

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“…Therefore, the magnetic characterization during fractionation was performed using optimized parameters (Bexc = 25 mT, tavg = 10 s, dV/dt = 100 µL/min) gained from preliminary experiments to obtain the highest sensitivity. The hydrodynamic separation was carried out on FER, which is known to have a polydisperse size distribution consisting of single crystallites and clusters [20][21][22][23]. Accordingly, this was also confirmed by the measured UV fractogram showing the presence of a bimodal distribution (Figure 6a) exhibiting two distinct maxima with retention coefficients R = t0/tr = 0.5 and 0.2, respectively.…”

Section: Mps Online Detectionmentioning

confidence: 56%

“…For a comprehensive analysis and higher stability of results, it is recomended to apply different excitation fields Bexc or frequencys f0 [17,18]. It was shown that the combination of A4F with magnetic characterization [19][20][21], or recently, using offline MPS, enables a more detailed study of size-dependent magnetic characteristics of MNPs [22,23].…”

Section: Introductionmentioning

confidence: 99%

Hyphenation of Field-Flow Fractionation and Magnetic Particle Spectroscopy

et al. 2015

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Magnetic nanoparticles (MNPs) exhibit unique magnetic properties making them ideally suited for a variety of biomedical applications. Depending on the desired magnetic effect, MNPs must meet special magnetic requirements which are mainly determined by their structural properties (e.g., size distribution). The hyphenation of chromatographic separation techniques with complementary detectors is capable of providing multidimensional information of submicron particles. Although various methods have already been combined for this approach, so far, no detector for the online magnetic analysis was used. Magnetic particle spectroscopy (MPS) has been proven a straightforward technique for specific quantification and characterization of MNPs. It combines high sensitivity with high temporal resolution; both of these are prerequisites for a successful hyphenation with chromatographic separation. We demonstrate the capability of MPS to specifically detect and characterize MNPs under usually applied asymmetric flow field-flow fractionation (A4F) conditions (flow rates, MNP concentration, different MNP types). To this end MPS has been successfully integrated into an A4F multidetector platform including dynamic ligth scattering (DLS), multi-angle light scattering (MALS) and ultraviolet (UV) detection. Our system allows for rapid and comprehensive characterization of typical MNP samples for the systematic investigation of structure-dependent magnetic properties. This has been demonstrated by magnetic analysis of the commercial magnetic resonance imaging (MRI) contrast agent Ferucarbotran (FER) during hydrodynamic A4F fractionation. OPEN ACCESSChromatography 2015, 2 656

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“…Magnetic Particle Spectroscopy (MPS), the zero-dimensional MPI, has been proven a straightforward technique to study the MPI performance of MNPs [2]. Generally, synthetic MNP preparation routes typically result in a more or less broad distribution of particle sizes with correspondingly different MPI performance [3]. Thus, it is difficult to identify the part of the distribution which contains the most suitable MPI tracer within a sample.…”

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confidence: 99%

Online coupling of hydrodynamic fractionation with DLS, MALLS and MPS for MPI tracer evaluation

Löwa

Radon

Wiekhorst

et al. 2015

2015 5th International Workshop on Magnetic Particle Imaging (IWMPI)

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INTRODUCTION: Currently, one of the main issues to improve the image quality of Magnetic Particle Imaging (MPI), besides the development of applicable MPI scanner systems and reconstruction methods, is the improvement of magnetic properties of magnetic nanoparticles (MNP), the so-called MPI tracer. Optimized tracers potentially enhance mass sensitivity and spatial resolution of MPI and may be the key for successful clinical MPI [1]. Magnetic Particle Spectroscopy (MPS), the zero-dimensional MPI, has been proven a straightforward technique to study the MPI performance of MNPs [2]. Generally, synthetic MNP preparation routes typically result in a more or less broad distribution of particle sizes with correspondingly different MPI performance [3]. Thus, it is difficult to identify the part of the distribution which contains the most suitable MPI tracer within a sample. To improve this situation we extended the in situ MPS-characterization of MPI tracers by online coupling to hydrodynamic separation (asymmetric flow field-flow fractionation, A4F) of MNP. The A4F-MPS setup was further equipped with online UV detection, dynamic light scattering (DLS) and multi angle laser light scattering (MALLS). Here, we report on the first results applying the extended MPS online detection in the A4F multi-detector setup using the MPI "gold-standard" Resovist®. METHODS:For the MPS online detection a capillary flow cell consisting of quartz glass with 3 turns in the sensitive measurement area (8x8 mm, V cell =8.9 μL) of the MPS (Bruker, GER) was manufactured. The flow cell was tested with respect to flow velocity dependent MPS signal changes using MNP of different sizes. The separation experiment was performed using the precursor of commercially available MNP Resovist ® (DDM128) purchased from Meito Sangyo (JPN). By A4F MNP were separated according to their size, with retention time that is directly proportional to hydrodynamic extension. The A4F (Postnova, GER) was connected directly to the UV detector ( =280 nm), the flow cell of the MALLS (PN3621, Postnova, GER) and the DLS (Zetasizer Nano ZS, Malvern, UK). Furthermore, MPS (B excite =25 mT, f excite =25 kHz) was directly coupled at the end of the detection line. RESULTS:The manufactured flow cell was capable of performing MPS measurements on MNP in flows up to 1 mL/min with no significant MPS signal change. When coupled to the A4F the temporal evolution of the MPS signal could be detected over a broad range of retention times and MNP sizes (see Fig.1). The application of the A4F multi-detector characterization of DDM128 confirmed the presence of a bimodal distribution of sizes which can be deduced from the UV trace (mainly proportional to the iron content) showing two distinct maxima at an elution volume of 4 mL and 11 mL. The hydrodynamic and cluster size measured by DLS and MALLS, respectively, linearly increased with retention time. The MPS signal represented by the third harmonic amplitude μ 3 ranging over two orders of magnitude did not correlate linearly with MNP size. The ...

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Hydrodynamic and magnetic fractionation of superparamagnetic nanoparticles for magnetic particle imaging

Cited by 19 publications

References 20 publications

Enhanced Methods to Estimate the Efficiency of Magnetic Nanoparticles in Imaging

Enhanced Methods to Estimate the Efficiency of Magnetic Nanoparticles in Imaging

Hyphenation of Field-Flow Fractionation and Magnetic Particle Spectroscopy

Online coupling of hydrodynamic fractionation with DLS, MALLS and MPS for MPI tracer evaluation

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