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Register a new userSimultaneous Magnetic Particle Imaging and Navigation of large superparamagnetic nanoparticles in bifurcation flow experiments
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Magnetic Particle Imaging (MPI) has been successfully used to visualize the distribution of superparamagnetic nanoparticles within 3D volumes with high sensitivity in real time. Since the magnetic field topology of MPI scanners is well suited for applying magnetic forces on particles and micron-sized ferromagnetic devices, MPI has been recently used to navigate micron-sized particles and micron-sized swimmers. In this work, we analyze the magnetophoretic mobility and the imaging performance of two different particle types for Magnetic Particle Imaging/Navigation (MPIN). MPIN constantly switches between imaging and magnetic modes, enabling quasi-simultaneous navigation and imaging of particles. We determine the limiting flow velocity to be 8.18 mL/s using a flow bifurcation experiment, that allows all particles to flow only through one branch of the bifurcation. Furthermore, we have succeeded in navigating the particles through the branch of a bifurcation phantom narrowed by either 60% or 100% stenosis, while imaging their accumulation on the stenosis. The particles in combination with therapeutic substances have a high potential for targeted drug delivery and could help to reduce the dose and improve the efficacy of the drug, e.g. for specific tumor therapy and ischemic stroke therapy.
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Magnetic nanoparticles (MNPs) exhibiting superparamagnetic properties might generate large magnetic dipole-dipole interaction with electron spins in organic semiconductors (OSECs). This concept could be considered analogous to the effect of hyperfine interaction (HFI). In order to investigate this model, Fe3O4 MNPs are used as a dopant for generating random hyperfine-like magnetic fields in a HFI-dominant {pi}-conjugated polymer host, poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MeH-PPV). The magnetoconductance (MC) response in organic light emitting diodes made by MeH-PPV/MNP blends is used to estimate the effective hyperfine field in the blends. Firstly, we find that the shape of the MC response essentially remains the same regardless of the MNP concentration, which is attributed to the similar functionality between the nuclear spins and the MNPs. Secondly, the width of MC increases with increasing MNP concentration. Magneto-optical Kerr effect experiments and micromagnetic simulation indicate that the additional increase of the MC width is associated with the strength of the magnetization of the blend. Finally, the MC broadening has the same temperature dependent trend as the magnetization of the MNPs where the unique effect of the MNPs in their superparamagnetic and ferromagnetic regimes on the MC response is observed. Magneto-photoinduced absorption (MPA) spectroscopy confirms that the MC broadening is not due to defects introduced by the MNPs, but is a result of unique superparamagnetic behavior. Our study yields a new pathway for tuning OSECs magnetic functionality, which is essential to organic optoelectronic devices and magnetic sensor applications.
Magnetic particle spectroscopy (MPS), also called magnetization response spectroscopy, is a novel measurement tool derived from magnetic particle imaging (MPI). It can be interpreted as a zero-dimensional version of MPI scanner. MPS was primarily designed for characterizing superparamagnetic iron oxide nanoparticles (SPIONs) regarding their applicability for MPI. In recent years, it has evolved into an independent, versatile, highly sensitive, inexpensive platform for biological and biomedical assays, cell labeling and tracking, and blood analysis. MPS has also developed into an auxiliary tool for magnetic imaging and hyperthermia by providing high spatial and temporal mappings of temperature and viscosity. Furthermore, other MPS-based applications are being explored such as magnetic fingerprints for product tracking and identification in supply chains. There are a variety of novel MPS-based applications being reported and demonstrated by many groups. In this short review, we highlighted some of the representative applications based on MPS platform, thereby providing a roadmap of this technology and our insights for researchers in this area.
To study the magnetic dynamics of superparamagnetic nanoparticles we use scanning probe relaxometry and dephasing of the nitrogen-vacancy (NV) center in diamond, characterizing the spin-noise of a single 10-nm magnetite particle. Additionally, we show the anisotropy of the NV sensitivitys dependence on the applied decoherence measurement method. By comparing the change in relaxation (T 1 ) and dephasing (T 2 ) time in the NV center when scanning a nanoparticle over it, we are able to extract the nanoparticles diameter and distance from the NV center using an Ornstein-Uhlenbeck model for the nanoparticles fluctuations. This scanning-probe technique can be used in the future to characterize different spin label substitutes for both medical applications and basic magnetic nanoparticle behavior.
We report on the magnetic and hyperthermia properties of iron nanoparticles synthesized by organometallic chemistry. They are 5.5 nm in diameter and display a saturation magnetization close to the bulk one. Magnetic properties are dominated by the contribution of aggregates of nanoparticles with respect to individual isolated nanoparticles. Alternative susceptibility measurements are been performed on a low interacting system obtained after eliminating the aggregates by centrifugation. A quantitative analysis using the Gittleman s model allow a determination of the effective anisotropy Keff = 1.3 * 10^5 J.m^{-3}, more than two times the magnetocristalline value of bulk iron. Hyperthermia measurements are performed on agglomerates of nanoparticles at a magnetic field up to 66 mT and at frequencies in the range 5-300 kHz. Maximum measured SAR is 280 W/g at 300 kHz and 66 mT. Specific absorption rate (SAR) displays a square dependence with the magnetic field below 30 mT but deviates from this power law at higher value. SAR is linear with the applied frequency for mu_0H=19 mT. The deviations from the linear response theory are discussed. A refined estimation of the optimal size of iron nanoparticles for hyperthermia applications is provided using the determined effective anisotropy value.
We present X-ray diffraction (XRD), Mossbauer spectroscopy (MS) and d.c. magnetization measurements performed on ball-milled CuFe2O4 samples. The average particle size <d> was found to decrease to the nanometer range after t=15 min of milling. Room temperature Mossbauer data showed that the fraction of particles above the blocking temperature TB increases with milling time, and almost complete superparamagnetic samples are obtained for <d> = 7(2) nm. Magnetization measurements below TB suggest spin canting in milled samples. The values of saturation moment mu_S reveal that site populations are slightly affected by milling. Mossbauer resonant intensities are accounted for on the basis of local disorder of Fe3+ environments, and the development of sample inhomogeneities of CuxFe3-xO4 composition.
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