Feasibility study of high-temperature thermoseed inductive hyperthermia in melanoma treatment.

Current treatment modalities for melanoma do not offer satisfactory efficacy. We have developed a new, minimally invasive hyperthermia technology based on radio-frequency hyperthermia. Herein, we investigated the feasibility of using a nickel-copper thermoseed for inductive hyperthermia at a relatively high temperature (46-55 ˚C). In vitro, the thermoseed showed good thermal effects and effective killing of B16/F10 melanoma cells. Temperatures of 53.1 ± 0.5 ˚C were achieved for a single thermoseed and 56.5 ± 0.5 ˚C for two in parallel (spacing 5 mm). No B16/F10 melanoma cells survived with heating time longer than 20 min in the parallel thermoseed group. Magnetic fields or thermoseeds alone did not affect the survival rate of B16/F10 cells (P>0.05). In vivo, B16/F10 melanoma cells were subcutaneously injected into the right axilla of C57BL/6 mice. After the tumors grew to ~11-13 mm, two thermoseeds (spacing 5 mm) were implanted into the tumors and the mice were subjected to an alternating magnetic field (100-250 kHz, 15 kA/m) to induce hyperthermia. The temperature at the center of the tumor reached 46 ˚C at 5 min and plateaued at 50 ˚C. Thermoseed treatment produced large necrotic areas, inhibited tumor growth in 60% (6 of 10) of animals and prolonged survival time (P<0.05). Thus, with further optimization and testing, high-temperature thermoseed inductive hyperthermia may have therapeutic potential for melanoma.

[Alternating magnetic field damages the reproductive function of murine testes].

OBJECTIVE: To explore the relationship between physical and biological effects of alternating magnetic field and study the influence of the magnetic field on the reproductive function of murine testes. METHODS: Thirty ICR mice were randomized into 5 groups: normal control, X-ray radiation, weak magnetic field (1000 Hz), 1 h strong magnetic field and 2 h strong magnetic field (2000 Hz). The mice were sacrificed at 7 days after the exposure for the analysis of testicular sperm motility, observation of histopathological changes in the testis by HE staining and evaluation of the changes by modified Johnsen grade criteria. RESULTS: The rates of sperm motility were (42.37 +/- 10.24)% in the normal control group, (39.00 +/- 12.35)% in the X-ray radiation group, (36.00 +/- 17.28)% in the weak magnetic field group, (10.72 +/- 5.67)% in the 1 h strong magnetic field group and (4.44 +/- 2.87)% in the 2 h strong magnetic field group, respectively. Johnsen's scores decreased and the testis damage increased in a dose- and time-dependent manner. CONCLUSION: Magnetic field, either strong or weak, may damage the testis function by inducing injury to seminiferous tubules and Leydig cells, thickening of the basal membrane, derangement, exfoliation, massive apoptosis and necrosis of spermatogenic cells in the lumen, situation of the epididymis, and consequently the absence of sperm.

[A method of showing thermal effect of iron oxide nanoparticles in alternating magnetic field].

BACKGROUND & OBJECTIVE: Ferromagnet has thermal effect in alternating magnetic field (AMF). Magnetically mediating hyperthermia is to localize magnetic substance within tumor tissue under AMF to promote the targeting ability and heat distribution of hyperthermia. This study was to develop a new method of showing the thermal effect of iron oxide Fe3O4 nanoparticles in AMF in vitro. METHODS: Melted polyethelene glycol (PEG) was dropped on a slide to form crystal monolayer after cooling, and was covered with a bipartite blood coverslip. Certain amount of Fe3O4 powder (average diameter, 10 nm) was added in the gap of the blood coverslip to form a strip wandering on the slide with the width of 0.5-1.0 mm. This apparatus, named analog vessel bed, was then alternated in a 4.6 mT AMF at 100-250 kHz for 15 min. The changes of PEG crystal images were observed under micropolariscope. The thermal range of the heated Fe3O4 powder was affirmed according to melting status and melting point value of PEG crystal. RESULTS: In AMF, 5 mg of Fe3O4 could rise the temperature to above 45 degrees C-50 degrees C, which exceeded the required hyperthermic temperature 43 degree C; 15 mg of Fe3O4 could rise the temperature to no more than 59 degrees C-61 degrees C; while 25 mg of Fe3O4 could be heated up to 59 degrees C-61 degrees C. The PEG melting area was enlarged with the increasing Fe3O4 quantity or decreasing PEG melting point. CONCLUSION: The analog vessel bed apparatus could display the thermal effect of Fe3O4 nanoparticles in AMF, and would be helpful for further studies on effect of magnetically mediated hyperthermia on cancer cells.