The Effect of an Alternating Magnetic Field and Silver Nanoparticles on the Spectral Characteristics of an Aqueous Solution of Human Serum Albumin

Biophysics - In this paper, we discuss experimental data obtained during study of the effect of a low-frequency alternating magnetic field on the conformational transitions of human serum albumin...     

Oxidative Damage to DNA under the Action of an Alternating Magnetic Field

The content of damaged 8-hydroxy-2-deoxyguanosine nitrogenous bases in the blood DNA of healthy donors and patients with epidermolysis bullosa after exposure to an alternating magnetic field of 550 ± 30 A/m in the frequency range from 3 to 60 Hz in vitro was determined using an enzyme immunoassay. The degree of oxidative DNA damage in epidermolysis bullosa was almost twice as high as in healthy donors. It was shown that there was a significant increase in the level of 8-oxoguanine in the DNA of both groups after the magnetic field treatment, which depended in a complex way on the frequency. The resulting effect is explained by the generation of reactive oxygen species under the influence of a magnetic field and the disruption of DNA repair processes.

     

铁蛋白纳米颗粒应用于生物医疗领域的研究进展

在漫长的进化过程中,生物系统中出现了多种多样的纳米粒子。其中铁蛋白纳米粒子广泛存在于所有生物体内,是参与生命活动的重要功能蛋白。近年来,铁蛋白自组装纳米粒子特殊的理化性质使其在生物医学领域应用中呈现出巨大的优势和应用前景。铁蛋白纳米笼的应用主要包括微量血清铁蛋白的临床检查、作为营养物质补充机体铁需求、纳米生物材料平台和纳米材料的生物呈递等。综述了铁蛋白纳米粒子在疾病诊断与治疗以及药物呈递与疫苗开发上的应用,并对铁蛋白纳米粒子在生物医学领域的应用前景进行展望。     

用铁蛋白合成纳米粒子的研究进展

铁蛋白是一种生物储铁蛋白 ,其储存铁的特性和储存铁在生物体内的特殊形态 ,通过相对温和、简便的生物、化学、物理过程 ,可合成多种具有特异的力、热、光、电、磁等特性的纳米粒子 ,并可用来构建纳米级的分子器件     

ELF Alternating Magnetic Field Decreases Reproduction by DNA Damage Induction

In the present experiments, the effect of 50-Hz alternating magnetic field on Drosophila melanogaster reproduction was studied. Newly eclosed insects were separated into identical groups of ten males and ten females and exposed to three different intensities of the ELF magnetic field (1, 11, and 21 G) continuously during the first 5 days of their adult lives. The reproductive capacity was assessed by the number of F₁ pupae according to a well-defined protocol of ours. The magnetic field was found to decrease reproduction by up to 4.3 %. The effect increased with increasing field intensities. The decline in reproductive capacity was found to be due to severe DNA damage (DNA fragmentation) and consequent cell death induction in the reproductive cells as determined by the TUNEL assay applied during early and mid-oogenesis (from germarium to stage 10) where physiological apoptosis does not occur. The increase in DNA damage was more significant than the corresponding decrease in reproductive capacity (up to ~7.5 %). The TUNEL-positive signal denoting DNA fragmentation was observed exclusively at the two most sensitive developmental stages of oogenesis: the early and mid-oogenesis checkpoints (i.e. region 2a/2b of the germarium and stages 7–8 just before the onset of vitellogenesis)—in contrast to exposure to microwave radiation of earlier work of ours in which the DNA fragmentation was induced at all developmental stages of early and mid-oogenesis. Moreover, the TUNEL-positive signal was observed in all three types of egg chamber cells, mainly in the nurse and follicle cells and also in the oocyte, in agreement with the microwave exposure of our earlier works. According to previous reports, cell death induction in the oocyte was observed only in the case of microwave exposure and not after exposure to other stress factors as toxic chemicals or food deprivation. Now it is also observed for the first time after ELF magnetic field exposure. Finally, in contrast to microwave exposure of previous experiments of ours in which the germarium checkpoint was found to be more sensitive than stage 7–8, in the magnetic field exposure of the present experiments the mid-oogenesis checkpoint was found to be more sensitive than the germarium.     

Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field

We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles.     

Alternating Magnetic Field Induced Membrane Permeability in Erythromycin Magneto-Liposomes A Potential Solution to Antibiotic Resistance

Biophysics - Antibiotic resistance is a serious problem facing the world; it is increasing every year due to over or misuse of antibiotics that led to developing new mechanisms of drug resistance...     

Increased Cellular Uptake of Biocompatible Superparamagnetic Iron Oxide Nanoparticles into Malignant Cells by an External Magnetic Field

Superparamagnetic iron oxide nanoparticles (SPIONs) are used as delivery systems for different therapeutics including nucleic acids for magnetofection-mediated gene therapy. The aim of our study was to evaluate physicochemical properties, biocompatibility, cellular uptake and trafficking pathways of the custom-synthesized SPIONs for their potential use in magnetofection. Custom-synthesized SPIONs were tested for size, shape, crystalline composition and magnetic behavior using a transmission electron microscope, X-ray diffractometer and magnetometer. SPIONs were dispersed in different aqueous media to obtain ferrofluids, which were tested for pH and stability using a pH meter and zetameter. Cytotoxicity was determined using the MTS and clonogenic assays. Cellular uptake and trafficking pathways were qualitatively evaluated by transmission electron microscopy and quantitatively by inductively coupled plasma atomic emission spectrometry. SPIONs were composed of an iron oxide core with a diameter of 8–9 nm, coated with a 2-nm-thick layer of silica. SPIONs, dispersed in 0.9% NaCl solution, resulted in a stable ferrofluid at physiological pH for several months. SPIONs were not cytotoxic in a broad range of concentrations and were readily internalized into different cells by endocytosis. Exposure to neodymium-iron-boron magnets significantly increased the cellular uptake of SPIONs, predominantly into malignant cells. The prepared SPIONs displayed adequate physicochemical and biomedical properties for potential use in magnetofection. Their cellular uptake was dependent on the cell type, and their accumulation within the cells was dependent on the duration of exposure to an external magnetic field.     

The Effect of an Alternating Magnetic Field on the Chemiluminescence of Human Peripheral Blood Mononuclear Cells and the Production of Pro-Inflammatory Cytokines

Biophysics - Abstract—It has been shown that in vitro exposure to an alternating magnetic field with a strength of 550 ± 30 A/m at a frequency of 8.6 and 9.0 Hz leads to a...     

外加磁场作用下磁性Fe3O4纳米粒子对肝癌细胞增殖和凋亡的影响

目的：观察磁性四氧化三铁（Fe3O4）纳米粒子对肝癌细胞的体外作用,并研究外加稳恒磁场（SMF）或交变磁场（EMF）对FeID4纳米粒子作用的影响。方法：光镜下观察CBRH-7919细胞对Fe3O4纳米粒子的吞噬作用;MTT法检测Fe304纳米粒子对大鼠肝癌细胞株CBRH-7919的毒性及外加磁场的影响;流式细胞术检测外加磁场作用下Fe3O4纳米粒子对细胞凋亡及线粒体膜电位的影响。结果：光镜下可见CBRH-7919细胞吞噬大量Fe3O4纳米粒子入胞浆,且交变磁场作用下细胞的吞噬量增加。30-100μg／mLFe3O4纳米粒子作用于CBRH-7919细胞未产生细胞毒性,稳恒磁场对其作用无影响,而交变磁场能增加Fe3O4纳米粒子的毒性,使细胞活性降低、凋亡率增加、线粒体膜电位降低。结论：交变磁场能增加CBRH-7919细胞对Fe3O4纳米粒子的吞噬并产生细胞毒性。     

磁性氧化铁纳米颗粒及其磁共振成像应用

磁性氧化铁纳米颗粒在磁共振成像方面的应用,已经在全世界范围内得到了广泛的关注,相关研究也被各国科学家高度重视.目前,磁性氧化铁纳米颗粒正在从早期的基于被动识别的肝部磁共振造影,快速转向基于主动识别的磁共振分子影像应用.本文将围绕磁性氧化铁纳米颗粒的生物体内应用,着重介绍磁性纳米颗粒的制备及其在疾病诊断,尤其是在肿瘤早期...     

Effects Silver Nanoparticles and Magnetic Field on Growth of Fodder Maize (Zea mays L.)

Two experiments were done in 2008 and 2009 to study the effects of magnetic field and silver nanoparticles on fodder maize (Zea mays L.). These experiments were done with seven treatments based on a randomized complete block design in four replications. The treatments were as follows: magnetic field and silver nanoparticles?+?Kemira fertilizer (T1), magnetic field and silver nanoparticles?+?Humax fertilizer (T2), magnetic field and silver nanoparticles (T3), Kemira fertilizer (T4), Librel fertilizer (T5), Humax fertilizer (T6), and a control (T7). Results showed that fresh yield was higher in treatments T3 and T4. Treatments T3 and T4 had increased maize fresh yields of 35 and 17.5?% in comparison to the control, respectively. The dry matter yield of those plants exposed to magnetic field and silver nanoparticles was significantly higher than that from any of the other treatments. Magnetic field and silver nanoparticle treatments (T3 and T1) showed higher percentages for ears, and the lowest percentages were found in treatments T7 and T5. In general, the soil conditions for crop growth were more favorable in 2009 than in 2008, which caused the maize to respond better to treatments tested in the study; therefore, treatments had more significant effects on studied traits in 2008 than in 2009.     

掺铁TiO2纳米颗粒与恒定磁场对HL60白血病肿瘤细胞的灭活效果

通过研究不同浓度、不同磁场作用下TiO2、掺铁TiO2纳米颗粒对HL60白血病细胞活性的影响,以及在接受光照和不接受光照条件下的细胞活性,探讨基于TiO2、掺铁TiO2纳米颗粒作为光敏剂的光动力疗法(PDT)灭活白血病肿瘤细胞的可行性.实验结果表明,纳米颗粒对细胞具有一定的抑制/毒性作用,纳米浓度越大,抑制/毒性作用越明显;磁场对细胞的毒性/抑制作用跟掺铁的浓度以及磁感应强度有关,掺铁纳米组在强磁场作用下对细胞抑制/毒性作用明显;此外,添加了纳米颗粒的PDT灭杀效率要比不添加纳米颗粒的PDT灭杀效率高.     

葡聚糖磁性纳米颗粒外加磁场对人树突状细胞基因转染效率的研究

目的研究葡聚糖磁性纳米颗粒（the dextran coated magnetic iron oxide nanoparticles,DMN）在外加钕一铁一硼稀土固定磁场的作用下对人树突状细胞转染效率以及安全性的影响。方法先通过磁力计对DMN进行分析;再将修饰有多聚赖氨酸（Poly-L—Lysine,PLL）的DMN携带绿色荧光蛋白pEGFP—Cl质粒报告基因,在钕-铁-硼稀土周定强磁场的作用下,体外转染人树突状细胞,用荧光显微镜直接观察和流式细胞仪检测来评价外加磁场对DMN作为人树突状细胞转染载体效率的影响;在转染后采用MTT比色法测定在磁场干预下的DMN对人树突状细胞增殖和功能的影响以了解其细胞毒性。结果DMN的核心直径〈30nm,具有明硅的超顺磁性,比饱和磁化强度也明显高于相同Fe3O4含量的普通磁块;DMN作为基因载体在外加磁场作用下,转染12h即可将报告基因转染至人树突状细胞内并成功表达,在荧光显微镜下可观察到绿色荧光细胞,24h转染率可达到最高（约为27％）,转染效率较未加磁场组提高了2～4倍。而且转染后的人树突状细胞增殖活性及功能未因DMN外加磁场及其作用时间的长短而受到影响。结论超顺磁性的DMN在外加磁场作用下可以明显、安全、有效地提高对人树突状细胞的转染效率。     

Nonequilibrium Magnetic Response of Anisotropic Superparamagnetic Nanoparticles and Possible Artifacts in Magnetic Particle Imaging

Magnetic responses of superparamagnetic nanoparticles to high-frequency AC magnetic fields with sufficiently large amplitudes are numerically simulated to exactly clarify the phenomena occurring in magnetic particle imaging. When the magnetic anisotropy energy inevitable in actual nanoparticles is taken into account in considering the magnetic potential, larger nanoparticles exhibit a delayed response to alternations of the magnetic fields. This kind of delay is rather remarkable in the lower-amplitude range of the field, where the assistance by the Zeeman energy to thermally activated magnetization reversal is insufficient. In some cases, a sign inversion of the third-order harmonic response was found to occur at some specific amplitude, despite the lack in DC bias magnetic field strength. Considering the attenuation of the AC magnetic field generated in the human body, it is possible that the phases of the signals from nanoparticles deep inside the body and those near the body surface are completely different. This may lead to artifacts in the reconstructed image. Furthermore, when the magnetic/thermal torque-driven rotation of the anisotropic nanoparticles as well as the magnetic anisotropy energy are taken into account, the simulated results show that, once the easy axes are aligned toward the direction of the DC bias magnetic field, it takes time to randomize them at the field-free point. During this relaxation, the third-order harmonic response depends highly upon the history of the magnetic field. This is because non-linearity of the anhysteretic magnetization curve for the superparamagnetic nanoparticles varies with the orientations of the easy axes. This history dependence may also lead to another artifact in magnetic particle imaging, when the scanning of the field-free point is faster than the Brownian relaxations.     

Ferritin as an exogenous yolk protein in snails

Summary A main yolk component in the oocytes of the pulmonate snailPlanorbarius corneus L. has been isolated and identified as the iron storage protein ferritin by its ultrastructure, iron content, immuunological properties and behaviour in disc electrophoresis. As judged from acrylamide electrophoresis data and ultrastructural observations, yolk ferritin is an exogenous protein which is synthesised in the hepatopancreas and taken up by the oocytes by endocytosis.     

Genetic and Maternal Variation for Heat Resistance in Drosophila from the Field

In Drosophila, field heritability estimates have focused on morphological traits and ignored maternal effects. This study considers heritable variation and maternal effects in a physiological trait, heat resistance. Drosophila were collected from the field in Melbourne, Australia. Resistance was determined using knock-down time at 37°. Drosophila melanogaster was more resistant than Drosophila simulans, and males tended to be more resistant than females. Field heritability and maternal effects were examined in D. simulans using the regression of laboratory-reared F(1) and F(2) onto field-collected parents. Males from the field were crossed to a laboratory stock to obtain progeny. The additive genetic component to variation in heat resistance was large and significant, and heritability was estimated to be around 0.5. A large maternal effect was also evident. Comparisons of regression coefficients suggested that the maternal effect was not associated with cytoplasmic factors. There was no correlation between body size (as measured by wing length) and heat resistance. Unlike in the case of morphological traits, the heritability for heat resistance in nature is not less than that measured in the laboratory.     

Silver Nanoparticles Toxicity and Bactericidal Effect Against Methicillin-Resistant Staphylococcus aureus: Nanoscale Does Matter

Silver nanoparticles, which are being used increasingly as antimicrobial agents, may extend its antibacterial application to methicillin-resistant Staphylococcus aureus (MRSA), the main cause of nosocomial infections worldwide. To explore the antibacterial properties of silver nanoparticles against MRSA, the present work includes an analysis of the relation between nanosilver effect and MRSA’s resistance mechanisms, a study of the size dependence of the bactericidal activity of nanosilver and a toxicity assessment of nanoparticles against epithelial human cells. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and MBC/MIC ratio of silver nanoparticles were quantified by using a luciferase-based assay. The cytotoxic effect (CC₅₀ and CC₉₀) of three different nanosilver sizes (10, 30–40, and 100 nm) were assessed in HeLa cells by a similar method. The therapeutic index was used as an indicator of nanosilver overall efficacy and safety. Silver nanoparticles inhibited bacterial growth of both MRSA and non-MR S. aureus in a bactericidal rather than a bacteriostatic manner (MBC/MIC ratio?≤?4). Silver nanoparticle’s therapeutic index varied when nanoparticle’s size diminished. At the same dose range, 10 nm nanoparticles were the most effective since they did not affect HeLa’s cell viability while inhibiting a considerable percentage of MRSA growth. Silver nanoparticles are effective bactericidal agents that are not affected by drug-resistant mechanisms of MRSA. Nanosilver size mediates MRSA inhibition and the cytotoxicity to human cells, being smaller nanoparticles the ones with a better antibacterial activity and nontoxic effect.