Gd-Doped Superparamagnetic Magnetite Nanoparticles for Potential Cancer Theranostics

Nanotechnology has facilitated the applications of a class of nanomaterials called superparamagnetic iron oxide nanoparticles (SPIONs) in cancer theranostics. This is a new discipline in biomedicine that combines therapy and diagnosis in one platform. The multifunctional SPIONs, which are capable of detecting, visualizing, and destroying the neoplastic cells with fewer side effects than the conventional therapies, are reviewed in this chapter for theranostic applications. The chapter summarizes the design parameters such as size, shape, coating, and target ligand functionalization of SPIONs, which enhance their ability to diagnose and treat cancer. The review discusses the methods of synthesizing SPIONs, their structural, morphological, and magnetic properties that are important for theranostics. The applications of SPIONs for drug delivery, magnetic resonance imaging, and magnetic hyperthermia therapy (MHT) are included. The results of our recent MHT study on Gd-doped SPION as a possible theranostic agent are highlighted. We have also discussed the challenges and outlook on the future research for theranostics in clinical settings

A method for measuring the Neel relaxation time in a frozen ferrofluid

We report a novel method of determining the average Neel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm +/- 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0 = 20 kA/m) driven at frequencies of 171 kHz, 232 kHz and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Neel relaxation time and estimate a room-temperature magnetocrystalline anisotropy constant of 40 kJ/m3, in agreement with previously published results

Tuning of the Magnetocrystalline Anisotropy in CoxFe3-xO4 Nanoparticles Through Cobalt Doping

We report on the effect of cobalt doping on the magnetocrystlline anisotropy of CoxFe3-xO4 nanopaticles. The CoxFe3-xO4 (

Magnetic and Optical Response of Tuning the Magnetocrysalline Anisotropy in Fe3O4 Nanoparticle Ferrofluids by Co Doping

CoxFe3−xO4 (0⩽x⩽0.10) nanoparticles coated with tetramethyl ammonium hydroxide as a surfactant were synthesized by a co-precipitation technique. The Fe:Co ratio was tuned up to x=0.10 by controlling the Co2+ concentration during synthesis. The mean particle size, determined by transmission electron microscopy, ranged between 15±4 and 18±4 nm. The superparamagnetic blocking temperature and the magnetocrystalline anisotropy constant of the ferrofluids, determined using ac and dc magnetic measurements, scale approximately linearly with cobalt concentration. We also find distinct differences in the optical response of different samples under an applied magnetic field. We attribute changes in field-induced optical relaxation for the x=0 and 0.05 samples to differences in the anisotropic microstructure under an applied magnetic field

A Method for Measuring the Néel Relaxation Time in a Frozen Ferrofluid

We report a novel method of determining the average Néel relaxation time and its temperature dependence by calculating derivatives of the measured time dependence of temperature for a frozen ferrofluid exposed to an alternating magnetic field. The ferrofluid, composed of dextran-coated Fe3O4 nanoparticles (diameter 13.7 nm ± 4.7 nm), was synthesized via wet chemical precipitation and characterized by x-ray diffraction and transmission electron microscopy. An alternating magnetic field of constant amplitude (H0=20H0=20 kA/m) driven at frequencies of 171 kHz, 232 kHz, and 343 kHz was used to determine the temperature dependent magnetic energy absorption rate in the temperature range from 160 K to 210 K. We found that the specific absorption rate of the ferrofluid decreased monotonically with temperature over this range at the given frequencies. From these measured data, we determined the temperature dependence of the Néel relaxation time and estimate a room-temperature magnetocrystalline anisotropy constant of 40 kJ/m3, in agreement with previously published results

Effects of Fatty Acid Surfactants on the Magnetic and Magnetohydrodynamic Properties of Ferrofluids

We prepared Fe 3 O 4 magnetic nanoparticles having diameters of approximately 12 nm by chemical coprecipitation, which were coated with three different fatty acid surfactants: oleic acid, lauric acid, and myristic acid. From x-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy measurements we confirmed that Fe 3 O 4 is the only phase present in the samples. The zero field cooled magnetization curves for the nanoparticles exhibit broad peaks, consistent with superparamagnetic blocking for the polydisperse samples, and a saturation magnetization smaller than that for bulk Fe 3 O 4 . Although there are minimal differences in the magnetic properties of the nanoparticles having different surfactants, we find significant changes in the hydrodynamic response depending on chain length. Hyperthermia measurements show considerably larger response for oleic acid-coated samples, while magneto-optical studies indicate that these samples have slower dynamics of aggregation under the influence of a dc field. These results suggest that the magnetohydrodynamic response of ferrofluids can be controlled by judiciously selecting appropriate surfactants

Optimization of Electrochemical Performance of LiFePO4/C by Indium Doping and High Temperature Annealing

We have prepared nano-structured In-doped (1 mol %) LiFePO4/C samples by sol–gel method followed by a selective high temperature (600 and 700 °C) annealing in a reducing environment of flowing Ar/H2 atmosphere. The crystal structure, particle size, morphology, and magnetic properties of nano-composites were characterized by X-ray diffraction (XRD), scanning electron microsopy (SEM), transmission electron microscopy (TEM), and 57Fe Mössbauer spectroscopy. The Rietveld refinement of XRD patterns of the nano-composites were indexed to the olivine crystal structure of LiFePO4 with space group Pnma, showing minor impurities of Fe2P and Li3PO4 due to decomposition of LiFePO4. We found that the doping of In in LiFePO4/C nanocomposites affects the amount of decomposed products, when compared to the un-doped ones treated under similar conditions. An optimum amount of Fe2P present in the In-doped samples enhances the electronic conductivity to achieve a much improved electrochemical performance. The galvanostatic charge/discharge curves show a significant improvement in the electrochemical performance of 700 °C annealed In-doped-LiFePO4/C sample with a discharge capacity of 142 mAh·g−1 at 1 C rate, better rate capability (~128 mAh·g−1 at 10 C rate, ~75% of the theoretical capacity) and excellent cyclic stability (96% retention after 250 cycles) compared to other samples. This enhancement in electrochemical performance is consistent with the results of our electrochemical impedance spectroscopy measurements showing decreased charge-transfer resistance and high exchange current density