ObjectiveTo investigate the bioeffects of extremely low frequency (ELF) magnetic field (MF) (50 Hz, 400μT) and magnetic nanoparticles (MNPs) via cytotoxicity and apoptosis assays on PC12 cells.
MethodsMNPs modified by SiO2 (MNP-SiO2) were characterized by transmission electron microscopy (TEM), dynamic light scattering and hysteresis loop measurement.PC12 cells were administrated with MNP-SiO2 with or without MF exposure for 48 h. Cytotoxicity and apoptosis were evaluated with MTT assay and annexin V-FITC/PI staining, respectively. The morphology and uptake of MNP-SiO2 were determined by TEM. MF simulation was performed by Ansoft Maxwell based on the finite element method.
ResultsMNP-SiO2 were identified as~20nm (diameter) ferromagnetic particles. MNP-SiO2reduced cell viability in a dose-dependent manner. MF also reduced cell viability with increasing concentrations of MNP-SiO2. MNP-SiO2 alone did not cause apoptosis in PC12 cells; instead, the proportion of apoptotic cells increased significantly under MF exposure and increasing doses of MNP-SiO2. MNP-SiO2 could be ingested andthen cause a slight change in cellmorphology.
ConclusionCombined exposure of MF and MNP-SiO2 resulted in remarkable cytotoxicity and increased apoptosis in PC12 cells. The results suggested that MF exposure couldstrengthen the MF of MNPs, which may enhance the bioeffects of ELF MF.

复合功能传递系统的结构、铁转递蛋白的传递联系和药物载体的磁性颗粒

This paper describes a new formulation of magnetic nanoparticles coated by a novel polymer matrixO-Carboxylmethylated Chitosan (O-CMC) as drug/gene carrier. The O-CMC magnetic nanoparticles were derivatized with a peptide sequence from the HIV-tat protein and transferrin to improve the translocational property and cellar uptake of the nanoparticles. To evaluate the O-MNPs-Tat-Tf as drug carriers, Methotrexate (MTX) was incorporated as a model drug and MTX-loaded O-MNPs-Tat-Tf with an average diameter of 75nm were prepared and characterized by TEM, AFM and VSM. The cytotoxicity of MTX-loaded O-MNPs-Tat-Tf was investigated with C6 cells. The results showed that the MTX-loaded O-MNPs-Tat-Tf retained significant antitumor toxicity; additionally, sustained release of MTX from O-CMC nanoparticles was observed in vitro, suggesting that the O-MNPs-Tat-Tf could be a novel magnetic targeting carrier. We also studied the ability of O-MNPs-Tat-Tf crossing BBB in rats by single photon emission computed tomography (SPECT).

C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene is a risk factor for stroke, suggesting that widespread detection could help to prevent stroke. DNA from 70 stroke pa-tients and 70 healthy controls was extracted from saliva using a magnetic nanoparticles-based method and from blood using conventional methods. Real-time PCR results revealed that the C677T polymorphism was genotyped by PCR using DNA extracted from both saliva and blood samples. The genotype results were confirmed by gene sequencing, and results for saliva and blood samples were consistent. The mutation TT genotype frequency was significantly higher in the stroke group than in controls. Homocysteine levels were significantly higher than controls in both TT genotype groups. Therefore, this noninvasive magnetic nanoparticles-based method using saliva samples could be used to screen for the MTHFR C677T polymorphism in target populations.

磁性纳米微粒在MR分子成像中的应用

0.1～100 nm属于纳米范畴,粒径在此范围内的颗粒即为纳米粒.近年来,随着化学、材料学等学科的发展,纳米技术在医学诊断检测、药物载体、生物治疗等方面显示出独特价值,并在一些实验研究中取得了令人瞩目的成绩[1-2],并由此产生了一门新兴的学科-纳米医学(nanomedicine).分子影像学技术是一项在分子或细胞水平上对生物体生理或病理变化进行成像的技术[3].MR是适于分子成像的技术之一,纳米技术与MR的结合使MR分子成像更具临床应用潜力[4].实现MR分子成像的关键是具备高敏感性、安全性和稳定性的分子探针.纳米粒具有独特的理化和生物学优势,是制备MR成像分子探针理想的载体.本文就纳米微粒在MR分子成像中的价值及其进展进行综述.