Hyperthermia is a minimally invasive approach to cancer treatment, but it is difficult to heat only the tumor without damaging surrounding tissue. To solve this problem, we studied the effectiveness of chemohyperthermia with docetaxel-embedded magnetoliposomes (DMLs) and an applied alternating current (AC) magnetic field. Human MKN45 gastric cancer cells were implanted in the hind limb of Balb-c/nu/nu mice. Various concentrations of docetaxel-embedded DMLs were injected into the tumors and exposed to an AC magnetic field (n 5 6, each). For comparison with hyperthermia alone, magnetite-loaded liposome (ML)-injected tumors were exposed to an AC magnetic field. Furthermore, the results of DML without AC treatment and docetaxel diluted into PBS with AC treatment were also compared (n 5 10, each). Tumor surface temperature was maintained between 42 and 43°C. Tumor volume was reduced in the DML group with a docetaxel concentration > 56.8 lg/ml, while a docetaxel concentration > 568.5 lg/ml was required for tumor reduction without hyperthermia. Statistically significant differences in tumor volume and survival rate were observed between the DML group exposed to the magnetic field and the other groups. The tumor disappeared in 3 mice in the DML group exposed to the magnetic field; 2 mice survived over 6 months after treatment, whereas all mice of the other groups died by 15 weeks. Histologically, hyperthermia with DML damaged tumor cells and DML diffused homogeneously. To the best of our knowledge, this is the first report to show that hyperthermia using chemotherapeutic agent-embedded magnetoliposomes has an anticancer effect.
Fine Mg1−xCaxFe2O4 ferrite powders for local thermal coagulation therapy were synthesized by a reverse coprecipitation method. The enhancement of temperature under an AC magnetic field was improved by the partial Ca2+ substitution. A high heat ability was obtained for the samples calcined at 300 and 800 °C.
We found that the nano-sized Y 3 Fe 5 O 12 powder prepared by bead milling has the highest heat generation ability in an AC magnetic field of reported superparamagnetic materials. The heat generation ability in an AC magnetic field was strongly improved by a decrease in the average crystallite size of the bead milled samples. The highest heat ability in the AC magnetic field was for the fine Y 3 Fe 5 O 12 powder with ca. 15 nm crystallite size (the samples milled for 4 h using 0.1 mmu beads). The reasons for the high heat generation properties of the milled samples are ascribed to an increase in the Ne´el relaxation of the superparamagnetic material. The heat generation ability (W·g À1 ) can be estimated using a 3.58 3 10 À4 f·H 2 frequency (f/kHz) and the magnetic field (H/kA·m À1 ) for the sample milled for 4 h using 0.1 mmu beads.
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