Using thermal energy produced by irradiation of Mn-Zn ferrite magnetic nanoparticles (MZF-NPs) for heat-inducible gene expression.

One of the main advantages of gene therapy over traditional therapy is the potential to target the expression of therapeutic genes in desired cells or tissues. To achieve targeted gene expression, we developed a novel heat-inducible gene expression system in which thermal energy generated by Mn-Zn ferrite magnetic nanoparticles (MZF-NPs) under an alternating magnetic field (AMF) was used to activate gene expression. MZF-NPs, obtained by co-precipitation method, were firstly surface modified with cation poly(ethylenimine) (PEI). Then thermodynamic test of various doses of MZF-NPs was preformed in vivo and in vitro. PEI-MZF-NPs showed good DNA binding ability and high transfection efficiency. In AMF, they could rise to a steady temperature. To analyze the heat-induced gene expression under an AMF, we combined P1730OR vector transfection with hyperthermia produced by irradiation of MZF-NPs. By using LacZ gene as a reporter gene and Hsp70 as a promoter, it was demonstrated that expression of a heterogeneous gene could be elevated to 10 to 500-fold over background by moderate hyperthermia (added 12.24 or 25.81 mg MZF-NPs to growth medium) in tissue cultured cells. When injected with 2.6 or 4.6 mg MZF-NPs, the temperature of tumor-bearing nude mice could rise to 39.5 or 42.8 degrees C, respectively, and the beta-gal concentration could increase up to 3.8 or 8.1 mU/mg proteins accordingly 1 day after hyperthermia treatment. Our results therefore supported hyperthermia produced by irradiation of MZF-NPs under an AMF as a feasible approach for targeted heat-induced gene expression. This novel system made use of the relative low Curie point of MZF-NPs to control the in vivo hyperthermia temperature and therefore acquired safe and effective heat-inducible transgene expression.

Effect of phosphorus-32 glass microspheres on human hepatocellular carcinoma in nude mice.

AIM: To study the effects of phosphorus-32 glass microspheres ((32)P-GMS) on human hepatocellular carcinoma in nude mice. METHODS: Human liver cancer cell line was implanted into the dorsal subcutaneous tissue of 40 BALB/c nude mice. Then the 40 tumor-bearing BALB/ c nude mice were allocated into treatment group (n=32) and control group (n=8). In the former group different doses of (32)P-GMS were injected into the tumor mass, while in the latter nonradioactive (31)P-GMS was injected into the tumor mass. The experimental animals were sacrificed on the 14th day. The ultrastructural changes of tumor in both treatment group and control group were studied with transmission electron microscopy (TEM) and stereology. RESULTS: In treatment group, a lot of tumor cells were killed and the death rate of tumor cells was much higher (35-70%). Ultrastructurally, severe nuclear damage was observed in the death cells. The characteristics of apoptosis such as margination of heterochromatin was also found in some tumor cells. Besides, well differentiated tumor cells, degenerative tumor cells and some lymphocytes were seen. The skin and muscle adjacent to the tumor were normal. In control group, the tumor consisted of poorly differentiated tumor cells, in which there were only a few of dead cells(5%). Stereological analysis of ultrastructural morphology showed that Vv of nuclei (53.31+/-3.46) and Vv of nucleoli(20.40+/-1.84) in the control group were larger than those(30.21+/-3.52 and 10.96+/-2.52) in the treatment group respectively (P<0.01), and Vv of RER (3.21+/-0.54) and Vv of mitochondria (4.53+/-0.89) in the control group were smaller than those (8.67+/-1.25 and 7.12+/-0.95) in the treatment group respectively (P<0.01, 0.05). Sv of the membrane of microvilli and canaliculi (27.12 um(2)/100 um(3)+/-11.84 um(2)/100 um(3)) in the control group was smaller than that (78.81 um(2)/100 um(3)+/- 19.69 um(2)/100 um(3)) in the treatment group (P<0.01). But Vv of lipid particles (3.71+/-1.97) and Vv of vacuoles (5.72+/-1.58) were much larger than those (0.30+/-0.16 and 0.35+/-0.15) in the treatment group respectively (P<0.05, P<0.01). CONCLUSION: The experimental results indicate that local administration of (32)P-GMS can produce obvious effect on liver cancer cells and the anticancer effect of (32)P-GMS is directly proportional to the dose administrated. Ultrastructural stereology can also show the effect of (32)P-GMS on the normalization of tumor cells, which is beneficial to the prognosis and treatment of patients. Moreover, local administration of (32)P-GMS is also safe.