聚乙二醇修饰的5-氟尿嘧啶磁性白蛋白微球联合恒定外磁场对体外人结肠癌细胞生长的抑制作用

目的探讨聚乙二醇修饰的磁性5-氟尿嘧啶白蛋白微球(PEG-5-FU-MAMS)联合恒定外磁场体外对人结肠癌(LoVo)细胞生长的抑制作用及其机制。 方法采用乳化-加热固化法制备PEG-5-FU-MAMS,并检测其表征,将体外培养的LoVo细胞分为4组：A组为PEG-5-FU-MAMS联合磁场组;B组为PEG-5-FU-MAMS组;C组为游离5-氟尿嘧啶(5-FU)组;D组为单纯磁场组。参照5-FU血浆峰水平10.0 mg/L,每组设含5-FU水平为1.0,2.0,5.0,10.0,20.0,50.0,100.0 mg/L 7种不同的药物和微球备用。每种条件重复3孔,采用噻唑蓝(MTT)比色分析法测定各组肿瘤细胞生长抑制率(IR),观察PEG-5-FU-MAMS联合恒定磁场组对体外LoVo细胞生长的抑制作用。 结果微球平均粒径为(1.32±0.50)μm,呈球形,表面光滑,载药量为(5.31±0.13)%,具有良好的磁响应性和缓释性。LoVo细胞培养24 h后,显微镜下各组肿瘤细胞完全贴壁,生长良好,折光性好。单纯磁场组体外对LoVo细胞生长无明显影响。经过不同的处理后,含5-FU浓度为20.0,50.0,100.0 mg/L时,B组和C组IR>50%,药物敏感,两组在相应药物浓度下IR相似,差异无统计学意义(q＝2.02,2.11,2.74;P>0.05)。在含5-FU浓度为10.0 mg/L时,A组IR为59.8%,IR>50%,药物敏感,且随着药物浓度的增高,IR逐步升高,与B、C组比较,差异有统计学意义(F＝62.09,66.74,56.62,66.13;P<0.05)。 结论PEG-5-FU-MAMS具有良好的外形、粒径、载药量、磁响应性和药物缓释作用;PEG-5-FU-MAMS联合恒定外磁场能显著增强对LoVo细胞生长的抑制效应。     

阿霉素磁性明胶微球的制备及靶向损毁脊髓背角镇痛作用的观察

目的：研究阿霉素磁性明胶微球的制备及特性检测，探讨其靶向损毁脊髓背角的镇痛作用。方法：采用乳化．交联法制备阿霉素磁性明胶微球。高倍显微镜观察微球粒径大小及形态，紫外分光光度法检测微球中阿霉素的含量，测定微球磁吸附率，计算求和值S，确定最佳投料比（药物：载体），绘制药物微球体外释放曲线。28只雄性新西兰兔，随机分为5组：假手术组（S组）4只；空白微球对照5mg组（C1组）、15mg组（C2组），阿霉素磁性明胶微球5mg组（A1组）、15mg组（A2组），每组各6只。在外磁场作用下蛛网膜下腔注射微球，连续观察家兔下肢的电痛阈、运动功能的变化，30d后取腰骶段脊髓作病理检查。结果：制备的阿霉素磁性明胶微球最佳投料比为1：15，磁吸附率为100％。微球外形圆整，分散性好。阿霉素60min释放75％左右，240min释放90％以上。A2组痛阈显著升高（P〈0．01），持续30d仍未见消失。所有家兔运动功能评分未见明显变化。A1组脊髓背角破坏轻微，A2组脊髓背角破坏明显，所有组的脊髓前角未见损毁。结论：制备的阿霉素磁性明胶微球缓释性好，磁响应性强，15mg组可靶向损毁脊髓背角，镇痛效应显著，具有“感觉．运动”分离作用，可作为疼痛治疗的靶向神经损毁剂。     

磁场联合阿霉素磁液靶向治疗鼠种植性胃肿瘤的实验研究

目的　探讨阿霉素磁液经消化道给药后，联合外磁场对鼠种植性胃肿瘤的靶向治疗作用机制。方法　利用Walker-256瘤细胞制作鼠种植性胃肿瘤模型，并分成阿霉素磁液联合外磁场的靶向组，单纯阿霉素治疗的非靶向组及空白对照组。观察动物的一般状况，肿瘤生长率，病理组织学改变及动物生存时间等变化。结果　与空白对照组比较，靶向组动物肿瘤生长明显缓慢，瘤重及瘤体积抑制率分别为78.08%和82.52%(χ     

阿霉素海藻酸钠微球栓塞对兔VX2肝移植瘤生长及转移影响的实验研究

目的研究阿霉素海藻酸钠微球对兔VX2肝移植瘤的化疗栓塞作用。方法30只新西兰大白兔,于肝左叶内植入VX2肿瘤组织块,建立肝移植瘤模型。实验动物随机分成5组,每组6只。各组实验动物均开腹游离肝动脉,经肝动脉楔入法分别给予生理盐水(A组)、空白海藻酸钠微球(B组)、阿霉素海藻酸钠微球(C组)、超液化碘油(D组)、超液化碘油+阿霉素(E组)。治疗后第3周将所有实验动物处死,取肿瘤标本进行病理组织学检查,测定不同处理组肿瘤生长率、坏死率、凋亡指数,并观察不同处理组肝内转移及远隔转移的影响。结果阿霉素海藻酸钠微球组明显抑制肿瘤生长,移植瘤坏死率高于空白微球组;在肝内及远隔转移方面,空白微球组及载药微球组抑制远隔转移方面较其他组优,两组间相比则无显著性差异(P>0.05)。阿霉素海藻酸钠微球组TUNEL阳性率最高,为(14.3±3.65)%。结论阿霉素海藻酸钠微球通过栓塞肿瘤供血动脉,局部缓慢释放化疗药物,可以提高兔VX2肝移植瘤模型的化疗效果。     

沙利霉素逆转P-gp介导的肾癌ACHN细胞多药耐药的实验研究

目的探讨沙利霉素对肾癌ACHN细胞多药耐药的逆转及其机制。方法实验分为对照组、阿霉素组、沙利霉素组及阿霉素和沙利霉素联合用药组,药物作用24h后,CCK-8方法检测肾癌细胞的生长活性,免疫细胞化学法检测肾癌细胞P-糖蛋白（P-gp）的表达情况。结果 10μg/ml阿霉素对肾癌ACHN细胞的生长抑制率仅为4.758%。沙利霉素组对肾癌ACHN细胞生长抑制率呈剂量依赖性,并高于阿霉素组（P〈0.05）,其中以10μmol/L组抑制率最高（达17.555%）。联合用药组的生长抑制率高于沙利霉素组及阿霉素组（P〈0.05）,以10μmol/L沙利霉素＋10μg/ml阿霉素组的抑制率最高（达45.447%）。与阿霉素组比较,经沙利霉素处理过的肾癌ACHN细胞中的P-gp蛋白表达下降（P〈0.05）。结论沙利霉素增强了肾癌ACHN细胞对阿霉素的敏感性,耐药性逆转的机制之一可能与沙利霉素下调癌细胞中P-gp的表达有关。     

超声联合SonoVue微泡介导NET-1siRNA转染人肝癌细胞

目的探讨超声联合微泡造影剂介导NET-1siRNA在人肝癌细胞中的转染效果。方法将培养的HepG2细胞分为5组:A组为空白对照;B组培养瓶中仅加入NET-1siRNA;C组为加入脂质体及NET-1siRNA;D组为加入造影剂及NET-1siRNA并给予超声辐照;E组为加入脂质体、造影剂、NET-1siRNA,并给予超声辐照。之后以荧光显微镜检测NET-1siRNA转染率,RT-PCR法检测各组细胞NET-1 mRNA的基因表达,Western-Blotting法检测各组细胞NET-1表达情况,MTT检测HepG2细胞生长情况。结果与C组、D组相比,E组NET-1siRNA转染率明显提高(P<0.05);D组和E组细胞内NET-1mRNA及NET-1蛋白的表达抑制率均高于其他各组(P均<0.01),而转染后24～72hHepG2细胞增殖受到明显抑制。结论超声联合微泡造影剂能有效促进NET-1siRNA在肝癌细胞中的表达,并抑制肝癌细胞的增殖。     

亚甲蓝磁性明胶微球在外磁场作用下对家兔痛阈及体感诱发电位的影响

背景:靶向给药系统是一种安全高效的药物传递途径和技术,是一种新的制剂技术和工艺,这种制剂能将药品运送到靶器官或靶细胞,而正常部位几乎不受药物的影响.目的:实验拟观察亚甲蓝磁性明胶微球在外磁场作用下对家兔痛阈及体感诱发电位的影响,探讨其对脊髓背根神经结靶向神经阻滞的可行性.设计、时间及地点:随机对照动物实验,于2004-03/2005-04在解放军总医院实验动物中心完成.材料:雄性新西兰兔24只,体质量2.3～2.8 kg:空白明胶微球(自制);亚甲蓝磁性明胶微球(自制,载药量为9.8%).微球系院内药理学实验室高级技师协助制备.干预:24只家兔随机数字表法分为亚甲蓝磁性微球15 mg组:在外磁场作用下家兔蛛网膜下腔注射亚甲蓝磁性明胶微球15 mg:空白磁性微球15 mg组注射单纯磁性微球15 mg:假手术对照组:麻醉和手术步骤同其他组,每组8只.主要观察指标:连续观察注射药物后家兔下肢的电痛阈、运动功能及脊髓体感诱发电位的变化,最后取脊髓腰骶端作病理切片观察.结果:24只新西兰兔均进入结果分析.①亚甲蓝磁性微球15 mg组家兔后肢电痛阈值在给药后第1～6天明显升高,与自身给药前及其他组相比,差异显著(P＜0.05).②亚甲蓝磁性微球15mg组家兔体感诱发电位N1波潜伏期第1～11天明显延长,与自身给药前及其他组相比,差异显著(P＜0.05):术后13 d恢复正常.③病理观察显示各组脊髓背角结构、形态正常,神经轴索排列正常,灰白质界限清楚,除假手术对照组外其他组背角均有少数未完全降解的微球,各组的脊髓前角可观察到形态正常的前角运动神经细胞及神经轴索,结构完整.结论:亚甲蓝磁性明胶微球在外磁场作用下可靶向阻滞脊髓背根神经结,提高家兔的痛阈并延长体感诱发电位,具有"感觉-运动"分离阻滞作用,是一种有效的长效靶向神经阻滞剂.     

超声介导载阿霉素微泡对小鼠H22肝癌皮下移植瘤抑制作用的实验研究

目的 探讨超声介导载阿霉素微泡对小鼠H22肝癌皮下移植瘤的抑制效果.方法 ①制备载阿霉素微泡,并检测其一般性质.②建立小鼠H22肝癌皮下移植瘤模型,将荷瘤小鼠随机分为对照组、空微泡+超声组、阿霉素组及阿霉素微泡+超声组,治疗5次后,绘制各组肿瘤生长曲线,计算抑瘤率,冰冻切片观察阿霉素在肿瘤组织的聚集情况,RT-PCR及...     

超声破坏载紫杉醇微泡对卵巢癌细胞株SKOV3的抑制增殖及诱导凋亡作用

目的探讨超声破坏载紫杉醇微泡后对卵巢癌细胞株SKOV3生长抑制及凋亡诱导作用。 方法体外培养卵巢癌细胞,将细胞分为5组,即紫杉醇组,紫杉醇联合超声辐照组,载紫杉醇微泡联合超声辐照组,单纯载紫杉醇微泡组及空白对照组。用MTT法观察超声破坏载紫杉醇微泡后在不同时间对细胞的生长抑制情况,用透射电镜观察细胞的凋亡诱导情况。 结果在紫杉醇浓度为1×10^-6mol/L时,载紫杉醇微泡联合超声组的细胞在微泡辐照击破后生长明显受到抑制,并且随培养时间延长,抑制效应越明显,透射电镜观察到载紫杉醇微泡联合超声组的细胞有凋亡小体,比其它各组对卵巢癌细胞株SKOV3的凋亡诱导作用强。 结论载紫杉醇微泡被超声辐照破坏后对卵巢癌细胞株SHKOV3生长有明显抑制作用,并且能诱导其凋亡。     

黄芩苷诱导T细胞淋巴瘤凋亡的初步研究

目的:探讨黄芩苷对T细胞淋巴瘤细胞的诱导调亡作用及其机制。方法:采用黄芩苷处理白血病细胞株Jurkat,3-(4,5-二甲基噻唑)-2,5-二苯基四氮唑溴盐法测定细胞生长抑制率,细胞甩片瑞氏染色法观察细胞形态学改变,流式细胞术检测细胞凋亡,蛋白印迹法检测凋亡相关蛋白天冬氨酸特异性半胱氨酸蛋白酶caspase-3、caspase-8、caspase-9及AKT/ERK-MYC信号通路的表达,并用Calcusyn软件分析其与阿霉素、环磷酰胺联合使用的药效。结果:黄芩苷作用于Jurkat细胞48 h后的半数抑制浓度(IC50)为(24.32±1.01)μg/mL,且其生长抑制作用呈药物浓度-时间依赖性。黄芩苷组细胞呈现细胞凋亡的形态学改变,流式细胞术检测凋亡细胞百分比亦明显高于对照组,且呈药物浓度依赖性,而这种作用可被pan-caspase抑制剂ZVAD-FMK逆转。黄芩苷作用于Jurkat细胞48 h后,活化剪切型caspase-3、caspase-8、caspase-9表达均上调,AKT/ERK-MYC通路被抑制。此外,黄芩苷与阿霉素联合使用具有显著的协同效应。结论:黄芩苷可有效抑制T细胞淋巴瘤细胞增殖,诱导内源性和外源性凋亡,抑制AKT/ERK-MYC信号通路,并与阿霉素有显著的协同效应,具有良好的临床应用前景。     

Magnetically responsive polycaprolactone nanocarriers for application in the biomedical field: magnetic hyperthermia,magnetic resonance imaging,and magnetic drug delivery

There are huge demands on multifunctional nanocarriers to be used in nanomedicine. Herein, we present a simple and efficient method for the preparation of multifunctional magnetically responsive polymeric-based nanocarriers optimized for biomedical applications. The hybrid delivery system is composed of drug-loaded polymer nanoparticles (poly(caprolactone), PCL) coated with a multilayer shell of polyglutamic acid (PGA) and superparamagnetic iron oxide nanoparticles (SPIONs), which are known as bio-acceptable components. The PCL nanocarriers with a model anticancer drug (Paclitaxel, PTX) were formed by the spontaneous emulsification solvent evaporation (SESE) method, while the magnetically responsive multilayer shell was formed via the layer-by-layer (LbL) method. As a result, we obtained magnetically responsive polycaprolactone nanocarriers (MN-PCL NCs) with an average size of about 120 nm. Using the 9.4 T preclinical magnetic resonance imaging (MRI) scanner we confirmed, that obtained MN-PCL NCs can be successfully used as a MRI-detectable drug delivery system. The magnetic hyperthermia effect of the MN-PCL NCs was demonstrated by applying a 25 mT radio-frequency (f = 429 kHz) alternating magnetic field. We found a Specific Absorption Rate (SAR) of 55 W g⁻¹. The conducted research fulfills the first step of investigation for biomedical application, which is mandatory for the planning of any in vitro and in vivo studies.

There are huge demands on multifunctional nanocarriers to be used in nanomedicine.     

Manipulation of light transmission from stable magnetic microrods formed by the alignment of magnetic nanoparticles

Due to the increasing energy consumption, smart technologies have been considered to automatically control energy loss. Smart windows, which can use external signals to modulate their transparency, can regulate solar energy by reflecting excess energy and retaining the required energy in a building without using additional energy to cool or heat the interiors of the building. Although many technologies have been developed for smart windows, they still need to be economically optimised. Here, we propose a facile method to synthesise magnetic microrods from magnetic nanoparticles by alignment using a magnetic field. To maximise the transparency difference in the ON and OFF states, we controlled the nanoparticle concentration in a dispersion liquid, magnetic field application time, and viscosity of the dispersant. Interestingly, the magnetic microrods remained stable when we mixed short-chain polymers (polyethylene glycol) with a liquid dispersant (isopropyl alcohol). Furthermore, the Fe₂O₃ microrods maintained their shape for more than a week, while the Fe₃O₄ microrods clustered after a day because they became permanent magnets. The anisotropic features of the magnetic rods were used as a light valve to control the transparency of the smart window.

Magnetic microrods were synthesised from magnetic nanoparticles by alignment using a magnetic field. The transparency difference was maximised and the anisotropic features of the rods were used as a light valve to control the transparency of a smart window.

Buildings, factories, and houses consume a considerable amount of energy resulting in energy shortages. In addition, the depletion of fossil fuels is threatening the current energy supply. Therefore, the smart window technology is considered for reducing the current energy consumption, because a “SMART” window can regulate solar energy.^1,2 When it is too sunny outside, for example, the window can block the sunlight to remove the need for operating cooling systems which consume electrical energy. In addition, the smart technology can be used to artificially control the transparency of windows, which enhances the comfort in automobiles and aircrafts. Many researchers have developed optimised materials that use external signals, such as temperature, electricity, or magnetic field to control their transmittance.^1–11 For example, electrochromic and thermochromic materials, such as nanocrystal and amorphous metal oxide composites, monolithic-phased vanadium dioxide (VO₂), and hydrogel microparticles, have been recently studied for use in smart windows. To adjust optical transmittance, nanocrystals embedded in metal oxide exploit their electrochemical charging and discharging,³ vanadium dioxide uses a reversible metal-to-insulator transition,⁴ and hydrogel microparticles control their diameter to modulate the light scattering by changing the temperature.⁵ Mechanoresponsive smart windows, which use the light scattering effects on particle-embedded films or micropillars, are also potential candidates for these applications.^6–8 In addition, the use of mechanoresponsive and electrically driven wrinkles on a surface has been proposed as a smart window to scatter the light.^9,10 Functional materials such as liquid crystals (LCs) and particles have been used to manipulate transmittance. Polymer-dispersed liquid crystals (PDLCs) modulate the alignment direction of LCs by applying electrical signals.^1,2,11 Suspended particle (SP)-based smart windows that utilise the alignment of microparticles to change their transmittance have also been used.^1,2 In addition, magnetic materials have been used to modulate transmittance.^12–14 The use of magnetically responsive elastomeric micropillar arrays has also been demonstrated for controlling the light.¹³ Previously, our group reported a smart window inspired by a squid skin that uses the movement of magnetic nanoparticles within a tapered structure to control its transparency.¹⁴ However, the switching time based on this movement was long for practical utilisation. Although many materials have been developed for smart windows, these materials still need to be economically optimised.Here, we introduce a facile method for preparing stable magnetic microrods that can be utilised for smart windows by changing the direction of the magnetic field. Therefore, we applied a magnetic field to align magnetic Fe₂O₃ nanoparticles to form magnetic microrods. These rods have high aspect ratios; therefore, they can be used as light valves to control light transparency. Furthermore, we examined the effect of the nanoparticle concentration, magnetic field application time, and dispersant fluid viscosity on the formation of these magnetic rods. We also assessed their stability via mechanical agitation. Finally, we compared the stability of the Fe₂O₃ rods with that of microrods formed from Fe₃O₄ nanoparticles. Fig. 1(a) shows a schematic illustration of the formation of the magnetic microrods by applying a magnetic field. Initially, we prepared the magnetic nanoparticles and dispersion liquid mixture; thereafter, we applied a magnetic field using a neodymium magnet for 10 to 30 minutes to obtain magnetic rods dispersed in liquid. The Fe₂O₃ nanoparticles used were ∼50 nm in diameter. Meanwhile, an isopropyl alcohol (IPA) and polyethylene glycol (PEG) (molecular weight = 300) mixture was used as the dispersion liquid. Once the rods were formed, the applied magnetic field was removed. The dispersion liquid was filled in a transparent cavity (4 cm × 4 cm × 3 mm); thereafter, the direction of the magnetic rods was switched by controlling the magnetic field. A detailed procedure of the transparent cavity preparation is described in the experimental section and ESI (Fig. S1^†). The smart window filled with magnetic rods was placed on a display device (Samsung Galaxy J7), and then, the device screen was examined through the window. When the magnetic rods were vertically oriented (Fig. 1(b)), the university logo shown on the screen could be seen through the transparent cavity filled with magnetic rods (Fig. 1(c)). As shown in the microscopic image in Fig. 1(d), the transparent region could be seen. The black region is the top view of the vertically oriented magnetic rods. When we switched the orientation of the magnetic rods (Fig. 1(e)), the display device screen could not be seen (Fig. 1(f)) because the magnetic rods were parallel to the substrate, making the whole region dark (Fig. 1(g)). Since the transmittance change originated from the rotation of the magnetic rods, a faster response to the magnetic field was achieved here than in our previous study. In the previous study, we used the movement of nanoparticles within a confined microstructure filled with a dispersant to induce the transmittance change.¹⁴ The real time switch of the transmittance is found in the ESI (Movie S1^†). To adjust the anisotropy features of the magnetic rods, we controlled the magnetic nanoparticle concentration, magnetic field application time, and dispersion liquid viscosity. Fig. 2(a) shows the display device screen through the smart window (thickness = 3 mm) filled with microrods formed by applying the magnetic field for 30 min at different magnetic nanoparticle concentrations. To control the concentration of nanoparticles, the mixing ratio of PEG and IPA was fixed at 4 : 6. At a concentration of 0.1 wt%, the screen was visible through the smart window in the OFF state; however, it darkened as the concentration increased. In contrast, at a concentration of 2 wt%, the screen in the ON state was dark. To measure the length of the magnetic rods, we placed one drop of a liquid on a glass slide and measured its length with a microscope (Fig. 2(b)). When the concentration increased, the length of the rod increased until the concentration reached 1 wt%. The rods clustered at a concentration of 2 wt%. Fig. 2(c) shows that the rod length is proportional to the concentration. The length of the rod at a concentration of 2 wt% was excluded because it could not be measured due to clustering. Fig. 2(d) shows the transmittance measured by a window tint metre (AT-173, Guangzhou Amittari Instruments Co., Ltd.) at different nanoparticle concentrations. The transmittance in the ON and OFF states decreased with increasing nanoparticle concentration. At a concentration of 0.5 wt%, the transmittances were 4.5% and 62% in the OFF and ON states, respectively.Open in a separate windowFig. 1(a) Schematic illustration of the formation of the magnetic microrods by applying a magnetic field. (b) Schematic illustration of magnetic rods vertically oriented by controlling the magnetic field. (c) Smart phone screen showing the university logo through the transparent cavity filled with magnetic rods. (d) Microscopic image of the vertically oriented magnetic rods. (e) Schematic illustration of magnetic rods oriented parallel to the surface by controlling the magnetic field. (f) Smart phone screen showing the university logo through the transparent cavity filled with magnetic rods when the rods are in parallel to the surface. (g) Microscopic image of the parallel oriented magnetic rods. The scale bars represent 100 μm.Open in a separate windowFig. 2(a) Pictures of the display screen through the smart window for different concentrations of magnetic nanoparticles. (b) Microscopic images of the microrods in different concentration. The scale bars represent 100 μm. (c) Graph of the magnetic rod lengths versus the magnetic nanoparticles concentration. (d) Graph of the transmittance under different concentration conditions. Fig. 3(a) depicts a graph of the length of the magnetic rods with respect to the magnetic field application time (the fixed concentration of magnetic particles = 0.5%, and the viscosity of dispersion liquids = 4.4 cPs). The rod length was proportional to the application time and saturated after approximately 30 min. The transmittance had a similar trend as that shown by the rod length, as shown in Fig. 3(b). To control the dispersion liquid viscosity, in this study, a mixture of low viscosity IPA and high viscosity PEG was used. We measured the liquid mixture viscosities at different ratios (see the ESI Fig. S2^†) using a rheometer (Rheometer R/S plus, Brookfield). The measured viscosities of IPA and PEG were 0.78 and 91 cPs, respectively. When we increased the fraction of the relatively viscous PEG, the viscosity increased. Fig. 3(c) shows the rod length under different liquid viscosity conditions (the concentration was fixed at 0.5 wt% and time at 30 min). When the viscosity was higher, the rod length decreased. As shown in Fig. 3(d), the transmittance had the same trend as that shown by the lengths of the magnetic rods. We note the experimental data in Fig. 1, ​,4,4, ​,5,5, and ​and66 were obtained in the optimized condition for forming microrods (concentration = 0.5 wt%, magnetic field applying time = 30 min, and the viscosity of dispersion liquids = 4.4 cPs).Open in a separate windowFig. 3(a) Graph showing the length of the magnetic rods with respect to the magnetic field application time. (b) Graph of the transmittance with respect to the magnetic field application time. (c) Graph of the rod length under different liquid viscosity conditions. (d) Graph of the transmittance under different liquid viscosity conditions.Open in a separate windowFig. 4(a) SEM image of the magnetic rods. (b) Graph showing the relation between the length of the magnetic rods and transmittance at a fixed concentration.Open in a separate windowFig. 5Photovoltaic measurement results in ON and OFF states in a smart window.Open in a separate windowFig. 6(a) Transmittance in the ON and OFF states before and after agitation with a vortex mixer for 30 s when IPA only and a mixture of IPA and PEG are used. (b) Microscopic image of the disassembled microrods formed in IPA only after mechanical agitation. (c) Microscopic image of the stable microrods formed in a liquid mixture after mechanical agitation. The scale bars represent 100 μm. (d) Schematic illustration of the PEG coating on the magnetic rods to stabilise them. (e) Transmittance in the ON and OFF states after making the magnetic rods and after 24 h when using Fe₂O₃ and Fe₃O₄. (f) Pictures in the ON and OFF states of a smart window filled with Fe₃O₄ microrods after leaving the sample for a day. (g) Microscopic image of the clustered Fe₃O₄ magnetic rods after a day. The scale bars in (b), (c), and (g) represent 100 μm. Fig. 4(a) shows a scanning electron microscope (SEM) image of the magnetic rods. The rod length and width were 50 and 6 μm, respectively, which implies that the aligned magnetic nanoparticles were parallel to each other to be grown in both directions to the magnetic field. The anisotropy of the microfeatures showed a transmittance change as the orientation changed, as shown in Fig. 2 and ​and3.3. When the number of nanoparticles is N, the number of rods is inversely proportional to the rod length l. When the magnetic rods are vertically oriented, the transmittance (T) can be derived using eqn (1) below.T ∼1 − αN/l1where α is the parameter incorporating the compactness of the nanoparticles, density, and the relationship between the vertical and parallel growths of the magnetic rods. Fig. 4(b) shows the experimental data and a graph, based on eqn (1), of the relationship between the length of the magnetic rods and the transmittance at a fixed concentration (0.5 wt%). At a longer rod length, the transmittance in the ON state was higher, as expected from eqn (1).To emphasize the possibility of regulation of solar energy which has a broad wavelength spectrum, we measured J–V curves with a photovoltaic cell in ON and OFF states of the smart window. We used a calibrated reference photovoltaic cell (91150-KG5) and placed the smart window on it. First, we measured the efficiency of the solar cell as a reference (4.92%), which used a window without nanoparticles. And then, we measured the efficiency of a solar cell covered by the smart window in the ON state (3.24%) and OFF state (0.43%), respectively (Fig. 5). The ON/OFF ratio of the efficiency of the solar cells was about 7.5 which could modulate the solar energy with a wide spectrum. It is also noted that we assumed that the regulation of thermal radiation is dominant in our smart windows because the concentration of magnetic nanoparticles is less than 2 wt%, which can be a small effect on conduction and convection of heat transfer between the windows.The formation of the linear magnetic chains or rods has been studied for decades by applying a magnetic field on the nanoparticles.^15–21 The aligned magnetic microfeatures can be incorporated into polymers to enhance their mechanical properties or promote their suitability for special uses or serve as nanometre-sized stir bars for mixing. The lengths of the magnetic chains were controlled by the magnetic field, nanoparticle concentration, and magnetic field application time. Other groups have shown that the chain length is proportional to the field strength, concentration, and magnetic field application time, which agrees with our experimental results.^15,16,21 Another important aspect in the formation of the magnetic chains is their stability. When formed in a polymer, the chains are cannot be moved after the polymer is cured.^17,18 However, when the magnetic chains are formed in a liquid, the chains can be disassembled after the magnetic field is removed. Another challenge is clustering when the microchains become permanent magnets. To maintain the aligned features of the magnetic chains, polymeric surfactants bonded to a colloid¹⁹ or silica encapsulating the chain are used after forming the magnetic chains.²⁰ The Velev group demonstrated flexible microfilaments by assembling lipid-coated iron oxide particles.²¹ These researchers explained that the filaments were formed by a combination of the dipole–dipole interparticle attraction and magnetophoretic attractions of the particles. In addition, these filaments were stable due to nanocapillary lipid binding. Their work can provide explanation to our experimental observations.In this study, we used viscous PEG (40 wt%) as one of the dispersion liquids in the mixture, which can hinder interparticle attraction for obtaining longer microrods. Therefore, the rod length was shorter when the PEG fraction was higher (Fig. 3(c–d)). PEG could have adhered to the surfaces of the nanoparticles and coated the entire surface of the microrods, making the magnetic rods stable even after the magnetic field was removed. To prove this, the magnetic rods formed in IPA only and those formed from the mixture were compared. After the formation of the magnetic rods, the transmittance values in the ON/OFF states of the two samples were measured. Thereafter, a vortex mixer (Genie2, Neolab) was used to mechanically vibrate (1380 rpm for 30 s) the magnetic rods. Fig. 6(a) shows the transmittance in the ON and OFF states before and after agitation. For the magnetic rods formed in IPA, the transmittances in the ON and OFF states were 45.8% and 4.7%, respectively. However, when we agitated them mechanically, the transmittance in the ON state reduced to 1.6%. On the other hand, for the magnetic rods formed in the liquid mixture (40% PEG), the transmittance did not change in the ON state even after mechanical agitation. Fig. 6(b and c) shows the microscopic images of the magnetic rods after 30 s of agitation. When we used IPA only, the magnetic rods disassembled after agitation (Fig. 6(b)) However, the rods maintained their shape when a mixture of PEG and IPA was used (Fig. 6(c)). Fig. 6(d) shows a schematic illustration of the formation of the stable magnetic rods. PEG plays a role as a stabiliser by coating the magnetic rods after they have been formed, thereby stabilizing them.For the ageing test, we prepared smart windows with magnetic rods formed from the Fe₂O₃ and Fe₃O₄ nanoparticles. After applying the magnetic field, the magnetic rods were formed in both cases. When the Fe₂O₃ nanoparticles were used, the transmittances in the ON/OFF states did not change after the sample was allowed to remain for 24 h (Fig. 6(e)). When Fe₃O₄ nanoparticles were used, however, the transmittances in the OFF states changed significantly (from 21.6% to 52.5%) after 24 h. Fig. 6(f) shows the display screen through the smart window filled with Fe₃O₄ microrods after 24 h in the ON and OFF states. The microrods were clustered and moved to the boundary. When we examined these magnetic rods in the dark region, as shown in Fig. 6(e), using a microscope, we found that the magnetic rods had clustered (Fig. 6(g)). Meanwhile, the magnetic rods formed from the Fe₂O₃ nanoparticles were stable even after one week. Liu et al. reported the magnetization (M) - magnetizing field (H) curves of Fe₂O₃ and Fe₃O₄ nanoparticles and they demonstrated that Fe₂O₃ showed superparamagnetism whereas Fe₃O₄ exhibited ferromagnetic behaviour.²² It can explain Fe₂O₃ microrods can be rotated by the magnetic field without clustering and Fe₃O₄ microrods are clustered because they became permanent magnets.     

Blood-flow magnetic resonance imaging of the retina

This study describes a novel MRI application to image basal blood flow, physiologically induced blood-flow changes, and the effects of isoflurane concentration on blood flow in the retina. Continuous arterial-spin-labeling technique with a separate neck coil for spin labeling was used to image blood flow of the rat retina at 90 x 90 x 1500-microm resolution. The average blood flow of the whole retina was 6.3+/-1.0 ml/g/min under 1% isoflurane, consistent with the high blood flow in the retina reported using other techniques. Blood flow is relatively constant along the length of the retina, except it dipped slightly around the optic nerve head and dropped significantly at the distal edges where the retina terminates. Hyperoxia (100% O(2)) decreased blood flow 25+/-6% relative to baseline (air) due to vasoconstriction. Hypercapnia (5% CO(2)+21% O(2)) increased blood flow 16+/-6% due to vasodilation. Increasing isoflurane (a potent vasodilator) concentration to 1.5% increased blood flow to 9.3+/-2.7 ml/g/min. Blood-flow signals were confirmed to be genuine by repeating measurements after the animals were sacrificed in the MRI scanner. This study demonstrates a proof of concept that quantitative blood flow of the retina can be measured using MRI without depth limitation. Blood-flow MRI has the potential to provide unique insights into retinal physiology, serve as an early biomarker for some retinal diseases, and could complement optically based imaging techniques.     

乳腺1H磁共振波谱(续)

对比增强MRI已经成为重要的乳腺成像手段,但是该手段并不总能提供确切的病理.在动态增强MRI基础上增加活体MRS的初步研究显示的结果很具前景,越来越多的研究小组将MRS加入乳腺MR扫描协议.本文阐明了进行MRS检查的预期检查结果,并列举了其中的一些缺陷.     

Normal magnetic resonance imaging of the thorax

The soft tissue contrast properties of magnetic resonance (MR) allow excellent discrimination of most intrathoracic structures other than the lungs, and allow good insight into normal anatomy. Using MR imaging, the normal cardiorespiratory system, including portions of the lungs and pleural spaces, as well as the mediastinal, chest wall, and cardiac structures can be well depicted. In addition, using newer MR pulse sequences, dynamic ECG-gated imaging can also be achieved, which allows a window into the normal functional processes of these organs.     

西门子磁共振技术进展

自1980年始,西门子医疗便致力于磁共振技术的发展.随着世界磁共振技术的迅速发展和市场的更高需求,西门子医疗磁共振事业部秉承核心理念,不断推陈出新,始终居于行业龙头位置.笔者从磁场强度、运行成本、开放性和舒适度、便利性、系统稳定性以及系统拓展性等几个方面详细解读西门子磁共振技术的卓越发展.     

乳腺1H磁共振波谱

对比增强MRI已经成为重要的乳腺成像手段,但是该手段并不总能提供确切的病理.在动态增强MRI基础上增加活体MRS的初步研究显示的结果很具前景,越来越多的研究小组将MRS加入乳腺MR检查序列.本文阐明了进行MRS检查的预期检查结果,并列举了其中的一些缺陷.     

Diffusion magnetic resonance imaging of the breast

Several studies have investigated the role of advanced magnetic resonance imaging (MRI) techniques, such as diffusion-weighted imaging (DWI), to improve the specificity of MRI for the evaluation of breast lesions. Potential roles for DWI and the apparent diffusion coefficient in characterizing breast tumors and distinguishing malignant from benign tissues have been reported. This article discusses the clinical applications of breast DWI, including literature results, technical issues and limitations, and the potential applications. The analysis of DWI at our institution is also discussed. The establishment of standard DWI protocols and diagnostic criteria is necessary to ensure accuracy and reproducibility at different centers.     

Cardiovascular magnetic resonance of the charcoal heart

We report a case of malignant melanoma metastasis to the heart presenting as complete heart block. The highlight of the case is to demonstrate that silent cardiac metastasis is not uncommon and CMR has the potential to characterize these cardiac metastases and should be used routinely as a screening tool for those cancers with a high chance of cardiac involvement.