| This paper presents water-based biocompatible fluids in which magnetite particles (Fe3O4) was coated with carboxymethyl chitosan orβ-cyclodextrin were prepared by means of one-step or two-step co-precipitation method. The coated nano-magnetic fluids (drug carrier) can be used as heating medium of magnetic hyperthermia. The experiment parameters of the two magnetic fluids were got by the repetitious technical experiments. The thermo-magnetic stabilities around induction heating in an alternating current (AC) magnetic field were investigated. Hyperthermia tests proved that the magnetic fluid is suitable for localized hyperthermia treatment of cancers.Firstly, A one-step method of preparing Fe3O4 magnetic nanoparticles coated with carboxymethyl chitosan was evaluated. The influence of the molar ratio value of Fe2+:Fe3+, amount of carboxymethyl chitosan and temperature was studied. The core-shell structures were characterized by Fourier transform infrared (FTIR). Thermo-gravimetric (TG), X-ray diffraction (XRD), Scanning electron microscope (SEM),Transmission electron microscope (TEM) and Vibration magnetometer (VSM) analysis. The adsorption behaviors, the effects on stability and magnetizations of nanoparticles were investigated. The adsorption characteristics between carboxymethyl chitosan and magnetite nanoparticles were analyzed. The coated magnetic fluids showed high saturate magnetism strength (σs= 2.1185 emu/g). The diameter of modified nanoparticles was approximately 25 nm.Secondly, water-based magnetic fluids were prepared by co-precipitation method usingβ-Cyclodextrin as coating agent. The influence to adsorption amount and particle stability of pH value, temperature, dosage of modified agent was got by the repetitious technical experiments. By characterized magnetic fluids, the size of bare magnetic particles is about 8 nm and the thickness of coating on the magnetite particles is about 21 nm.The magnetic fluids are stable and can disperse in water very well. The magnetic fluids'magnetic saturation intensionσs can reach to 1.7805 emu/g.Finally, The thermo-magnetic stabilities around induction heating under high-frequency alternating magnetic field with the oscillation frequency (50KHz) and the output current(450A) was investigated by placed magnetic fluids in the heater coil. The results showed that the heating rate increases with saturation of magnetic fluids and the temperature can rise over 41℃in high-frequency alternating magnetic field. It is showed that the magnetic fluids have a good heating effect, high thermo-magnetic stability and magnetic properties of magnetic fluids didn't change before and after induction heating. The magnetic fluids can be used for magnetic heat flow-meter on cancer.
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