Magnetic nanoparticles for enhancing the effectiveness of ultrasonic hyperthermia

Ultrasonic hyperthermia is a method of cancer treatment in which tumors are exposed to an elevated cytotoxic temperature using ultrasound (US). In conventional ultrasonic hyperthermia, the ultrasound-induced heating in the tumor is achieved through the absorption of wave energy. However, to obtain appropriate temperature in reasonable time, high US intensities, which can have a negative impact on healthy tissues, are required. The effectiveness of US for medical purposes can be significantly improved by using the so-called sonosensitizers, which can enhance the thermal effect of US on the tissue by increasing US absorption. One possible candidate for such sonosensitizers is magnetic nanoparticles with mean sizes of 10–300 nm, which can be efficiently heated because of additional attenuation and scattering of US. Additionally, magnetic nanoparticles are able to produce heat in the alternating magnetic field (magnetic hyperthermia). The synergetic application of ultrasonic and magnetic hyperthermia can lead to a promising treatment modality

Low-Temperature Preparation of Superparamagnetic CoFe2O4 Microspheres with High Saturation Magnetization

Based on a low-temperature route, monodispersed CoFe2O4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe2O4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe2O4 MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role

Acoustic Wave Propagation in Mercury in Constant External Magnetic Field

The paper gives a theoretical analysis of the effect of an external constant magnetic field on the propagation of ultrasonic waves in electrically conducting liquids as well as the results of measurements carried out in mercury. The theoretical part is based on Euler's equation, the equation of continuity, the thermodynamical equation, and Maxwell,s equations. In the experimental part we propose and apply two methods for the measurement of the ultrasonic propagation velocity and its variations, as well as a pulse method perfected by the use of analog memory for the determination of the amplitude absorption coefficient. The correctness of the theoretical basis underlying the calculation of the small changes in propagation velocity induced by the magnetic field is confirmed by experiment. The amplitude absorption coefficient determined experimentally is considerably greater than that calculated theoretically for the medium studied

Hysteresis of changes of ultrasonic wave absorption coefficient in a magnetic fluid caused by the magnetic field

Abstract The magnetic fluids change their structure under the influence of an external magnetic field and do not return to the initial state after the magnetic field removal. It is supposed that the cluster formed in the fluid subjected to a magnetic field remains after the field has been removed. The resulting dependence of the ferrofluid properties on its magnetic history has been studied by the analysis of changes in the ultrasonic wave absorption coefficient.