Brain Tumor Diagnostics and Therapeutics with Superparamagnetic Ferrite Nanoparticles

Ferrite nanoparticles (F-NPs) can transform both cancer diagnostics and therapeutics. Superparamagnetic F-NPs exhibit high magnetic moment and susceptibility such that in presence of a static magnetic field transverse relaxation rate of water protons for MRI contrast is augmented to locate F-NPs (i.e., diagnostics) and exposed to an alternating magnetic field local temperature is increased to induce tissue necrosis (i.e., thermotherapy). F-NPs are modified by chemical synthesis of mixed spinel ferrites as well as their size, shape, and coating. Purposely designed drug-containing nanoparticles (D-NPs) can slowly deliver drugs (i.e., chemotherapy). Convection-enhanced delivery (CED) of D-NPs with MRI guidance improves glioblastoma multiforme (GBM) treatment. MRI monitors the location of chemotherapy when D-NPs and F-NPs are coadministered with CED. However superparamagnetic field gradients produced by F-NPs complicate MRI readouts (spatial distortions) and MRS (extensive line broadening). Since extracellular pH (pHe) is a cancer hallmark, pHe imaging is needed to screen cancer treatments. Biosensor imaging of redundant deviation in shifts (BIRDS) extrapolates pHe from paramagnetically shifted signals and the pHe accuracy remains unaffected by F-NPs. Hence effect of both chemotherapy and thermotherapy can be monitored (by BIRDS), whereas location of F-NPs is revealed (by MRI). Smarter tethering of nanoparticles and agents will impact GBM theranostics

Synergistic use of thermogravimetric and electrochemical techniques for thermodynamic study of TiOx (1.67 <= x <= 2.0) at 1573 K

A thermodynamic study of the Ti-O system at 1573 K has been conducted using a combination of thermogravimetric and emf techniques. The results indicate that the variation of oxygen potential with the nonstoichiometric parameter delta in stability domain of TiO2-delta with rutile structure can be represented by the relation, Delta mu o(2) = -6RT In delta - 711970(+/-1600) J/mol. The corresponding relation between non-stoichiometric parameter delta and partial pressure of oxygen across the whole stability range of TiO2-delta at 1573 K is delta proportional to P-O2(-1/6). It is therefore evident that the oxygen deficient behavior of nonstoichiometric TiO2-delta is dominated by the presence of doubly charged oxygen vacancies and free electrons. The high-precision measurements enabled the resolution of oxygen potential steps corresponding to the different Magneli phases (Ti-n O2n-1) up to n = 15. Beyond this value of n, the oxygen potential steps were too small to be resolved. Based on composition of the Magneli phase in equilibrium with TiO2-delta, the maximum value of n is estimated to be 28. The chemical potential of titanium was derived as a function of composition using the Gibbs-Duhem relation. Gibbs energies of formation of the Magneli phases were derived from the chemical potentials of oxygen and titanium. The values of -2441.8(+/-5.8) kJ/mol for Ti4O7 and -1775.4(+/-4.3) kJ/mol for Ti3O5 Obtained in this study refine values of -2436.2(+/-26.1) kJ/mol and-1771.3(+/-6.9) kJ/mol, respectively, given in the JANAF thermochemical tables

Synergistic use of thermogravimetric and electrochemical techniques for thermodynamic study of TiO_x (1.67 &#8804;x&#8804; 2.0) at 1573 K

A thermodynamic study of the Ti-O system at 1573 K has been conducted using a combination of thermogravimetric and emf techniques. The results indicate that the variation of oxygen potential with the nonstoichiometric parameter δ in stability domain of TiO2-δ with rutile structure can be represented by the relation, ΔµO2=-6RT ln δ -711970(± 1600) J/mol. The corresponding relation between non-stoichiometric parameter δ and partial pressure of oxygen across the whole stability range of TiO2-δ at 1573 K is δ ∝ PO2-1/6. It is therefore evident that the oxygen deficient behavior of nonstoichiometric TiO2-δ is dominated by the presence of doubly charged oxygen vacancies and free electrons. The high-precision measurements enabled the resolution of oxygen potential steps corresponding to the different Magneli phases (TinO2n-1) up to n=15. Beyond this value of n, the oxygen potential steps were too small to be resolved. Based on composition of the Magneli phase in equilibrium with TiO2-δ, the maximum value of n is estimated to be 28. The chemical potential of titanium was derived as a function of composition using the Gibbs-Duhem relation. Gibbs energies of formation of the Magneli phases were derived from the chemical potentials of oxygen and titanium. The values of -2441.8(± 5.8) kJ/mol for Ti4O7 and -1775.4(± 4.3) kJ/mol for Ti3O5 obtained in this study refine values of -2436.2(± 26.1) kJ/mol and -1771.3(± 6.9) kJ/mol, respectively, given in the JANAF thermochemical tables

Synergistic Use of Thermogravimetric and Electrochemical Techniques for Thermodynamic Study of TiOxTiO_x (1.67≤ x≤ 2.0) at 1573 K

A thermodynamic study of the Ti-O system at 1573 K has been conducted using a combination of thermogravimetric and emf techniques. The results indicate that the variation of oxygen potential with the nonstoichiometric parameter δ in stability domain of $TiO_{2-\delta}$ with rutile structure can be represented by the relation, $\Delta \mu O_2=-6RT$ ln δ -711970(± 1600) J/mol. The corresponding relation between non-stoichiometric parameter δ and partial pressure of oxygen across the whole stability range of $TiO_{2-\delta}$ at 1573 K is δ ∝ PO2-1/6. It is therefore evident that the oxygen deficient behavior of nonstoichiometric of $TiO_{2-\delta}$ is dominated by the presence of doubly charged oxygen vacancies and free electrons. The high-precision measurements enabled the resolution of oxygen potential steps corresponding to the different Magneli phases $(Ti_nO_{2n-1})$ up to n=15. Beyond this value of n, the oxygen potential steps were too small to be resolved. Based on composition of the Magneli phase in equilibrium with of $TiO_{2-\delta}$, the maximum value of n is estimated to be 28. The chemical potential of titanium was derived as a function of composition using the Gibbs-Duhem relation. Gibbs energies of formation of the Magneli phases were derived from the chemical potentials of oxygen and titanium. The values of -2441.8(± 5.8) kJ/mol for $Ti_4O_7$ and -1775.4(± 4.3) kJ/mol for $Ti_3O_5$ obtained in this study refine values of -2436.2(± 26.1) kJ/mol and -1771.3(± 6.9) kJ/mol, respectively, given in the JANAF thermochemical tables

Investigation of various magnetic features of spinel type cobalt ferrite (CoFe2O4) nanoparticles tuned by annealing temperature

Cobalt ferrite (CoFe2O4) nanoparticles synthesized by chemical co-precipitation method were studied to see the effect of annealing temperatures on the structural parameters and magnetic properties of the sample. X-ray powder diffraction (XRD), transmission electron microscope (TEM) and SAD pattern demonstrated that single face (fcc) spinel structure of CoFe2O4 has been formed showing particles in completely crystalline state which was further confirmed by the lattice parameter and the unmixed hkl values. The particle size is in the range of about 5-10 nm depending on the annealing temperature from 200°C to 400°C. The grain growth occurred monotonically with the increase of annealing temperature. The magnetic properties demonstrated a strong dependence on particle size. The saturation magnetization Ms, remanent ratio Mr/Ms and coercivity Hc increased with the increase of particle size. The hysteresis curves for samples of different grain size showed the ferrimagnetic behavior which is completely analogous to the slow relaxation sextet peaks of Mössbauer spectroscopy. Other parameters such as chemical shift, quadruple splitting and hyperfine field and site occupancy of Fe3+ were determined by Mössbauer spectroscopy. Ferrimagnetic to superparamagnetic transition temperature known as blocking temperature TB was determined from the temperature dependent magnetization curves. With the increase of grain size, Blocking temperature also increases. Maximum entropy changes due to magnetic phase transition were also observed for mentioned annealing temperatures in the context of Magnetocaloric effect

Ultra-soft magnetic properties and correlated phase analysis by 57Fe Mössbauer spectroscopy of Fe74Cu0.8Nb2.7Si15.5B7 alloy

A detailed study of magnetic softness has been performed on FINEMENT type of ribbons by investigating the BH loop with maximum applied field of 960 A/m. The ribbon with the composition of Fe74Cu0.8Nb2.7Si15.5B7 was synthesized by rapid solidification technique and the compositions volume fraction was controlled by changing the annealing condition. Detail phase analysis was performed through X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Vibrating sample magnetometer (VSM) and Mössbauer spectroscopy in order to correlate the ultrasoft magnetic properties with the volume fraction of amorphous and α-Fe(Si) soft nano composites. Bright (BF) and dark field (DF) image with selective area diffraction (SAD) patterns by the transmission electron microscopy (TEM) of the sample annealed for the optimized annealed condition at 853 K for 3 min reveals nanocrystals with an average size between 10-15 nm possessing the bcc structure which matches with the grain size revealed by the X-ray diffraction. Kinetics of crystallization of α-Fe(Si) phases has been determined by DSC curves. Extremely small coercivity of 30.9 A/m and core loss of 2.5 W/Kg for the sample annealed at 853 K for 3 min was found. Similar values for other crystalline conditions were determined by using BH loop tracer with a maximum applied field of around 960 A/m. Mössbauer spectroscopy was used to determine chemical shift, hyperfine field distribution (HFD), and peak width of different phases. The volume fractions of the relative amount of amorphous and crystalline phases are also determined by Mössbauer spectroscopy. High saturation magnetization along with ultrasoft magnetic properties exhibits very high potentials technological applications

Effect of synthesis methods and a comparative study of structural and magnetic properties of zinc ferrite

Zinc ferrite samples were prepared by two different routes which are chemical co-precipitation and standard solid state double sintering method. Structural properties of ZnFe2O4 were determined, and initial particle size was found as 5 nm in the samples prepared by chemical co-precipitation technique. The XRD patterns showed the single phase of ZnFe2O4 spinel structure and confirmed by the lattice parameter and the unmixed hkl values for both the synthesis techniques. M-H curves at room temperature showed superparamagnetic nature of the samples sintered from 200°C to 600°C, synthesized by chemical co-precipitation technique. The Mössbauer analysis at room temperature showed a doublet which is the signature of superparamagnetic nature, and it is in agreement with the acquired M-H curves. The magnetization of ZnFe2O4 synthesized by chemical co-precipitation method was found higher than the magnetization of ZnFe2O4 synthesized by the solid-state double sintering method in the sintering temperature from 1100°C to 1300°C

Synthesis and characterization of Fe- and Co-based ferrite nanoparticles and study of the T-1 and T-2 relaxivity of chitosan-coated particles

In pursuit of newer and more effective contrast agents for magnetic resonance imaging, we report in this article the use of biocompatible chitosan-coated ferrite nanoparticles of different kinds with a view to determine their potential applications as the contrast agents in the field of nuclear magnetic resonance. The single-phase ferrite particles were synthesized by chemical co-precipitation (CoFe2O4 and Fe3O4) and by applying ultrasonic vibration (CoFe2O4 and Co0.8Zn0.2Fe2O4). Although magnetic anisotropy of CoFe2O4 nanoparticle leads to finite coercivity even for nanoensembles, it has been reduced significantly to a minimum level by applying ultrasonic vibration. Fe3O4 synthesized by chemical co-precipitation yielded particles which already possess negligible coercivity and remanence. Substitution of Co by Zn in CoFe2O4 increases the magnetization significantly with a small increase in coercivity and remanence. Particles synthesized by the application of ultrasonic vibration leads to the higher values of T-2 relaxivities than by chemical coprecipitation. We report that the T-2 relaxivities of these particles are of two orders of magnitude higher than corresponding T-1 relaxivities. Thus, these particles are evidently suitable as contrast agent for T-2 weighted MR images

Superparamagnetic behaviour and T-1, T-2 relaxivity of ZnFe2O4 nanoparticles for magnetic resonance imaging

In the present study, ZnFe2O4 nanoparticles were synthesized by the chemical co-precipitation followed by calcinations at 473 and 673K for 4h. Particle sizes obtained were 4 and 6nm for the calcination temperatures of 473 and 673K, respectively. To study the origin of system's low temperature spin dynamic behaviour, temperature dependence of susceptibility was investigated as a function of particle size and frequency. Slight increase in the grain size from 4nm at 473K to 6nm at 673K has led to a peak shift of temperature dependence of susceptibility measured at a constant frequency of 400Hz. Temperature dependence of at different frequencies also resulted in peak shift. Relaxation time dependence of peak temperature obeys a power law, which provides the fitting parameters within the range of superparamagnetic nature of the particles. Further, dependence of relaxation time and peak temperature obeys VogelFulcher law rather than NeelBrown equation demonstrating that the particles follow the behaviour of superparamagnetism of slightly interacting system. Spinlattice, T-1 and spinspin, T-2 relaxivity of proton of the water molecule in the presence of chitosan-coated superparamagnetic ZnFe2O4 nanoparticle yields the values of 0.002 and 0.360s(1)perppm