这项工作是由ICT R＆MSIP / IITP，大韩民国（:B0132-15-1001，下一步成像系统的开发批准号）的D程序的支持。

1.设计一个平面FMMD测量头<ol><li>选择的测量头线圈方案。根据图1选择的结构，由两个拾取线圈上面和两个样品下面的（ - ，+，+， - ）序列，与样品坐在两个（+），线圈之间的中心。该标志表示绕组， 即顺时针方向和方向，（+），（ - ）为逆时针方向。由此，拾取线圈的灵敏度变整个样品厚度几乎是均匀的。 <ol><li>放置励磁线圈，使得在拾取线圈直接感应信号，以防止前置放大器的饱和，实现到样品最大灵敏度抵消。满足这些基本的设计规则其它构造可设计。 </li></ol></li><li>指定最大样品厚度。在这里，使用2毫米。 <ol><li>选择拾取线圈的直径和长度类似于最大样本thickness。这里，为2毫米的内径被选择，这将产生3.7毫米为1.7mm绕组的高度的平均直径。线圈宽度为4mm。 </li><li>选择导线直径和拾取线圈这样的绕组数，所有拾取线圈的总阻抗大致匹配的前置放大器的输入阻抗。这个条件强加的检测次数的限制。在运算放大器与1100Ω最佳的输入阻抗，这样所有四个线圈拾音器有0.08毫米直径600绕组。漆包线，得到95.3Ω的总欧姆串联电阻和1.9毫亨，这给919Ω阻抗的总电感。 </li></ol></li><li>制备高频激磁线圈17，使得在该示例的位置的磁场理想地达约0.5 mT的。例如，如果线圈的内径为3.8毫米，宽度为8.5毫米，风粒径约0.1mmφ476绕组瓦特<html>愤怒。在这里，0.4 mT的一场场在f 1 = 76550赫兹达到了。 </li><li>准备低频激磁线圈17，使得在该示例的位置的磁场约为5 mT的。例如，如果线圈的内半径为5毫米，宽度为8.5毫米，风0.12毫米直径导线2000绕组。设置产生500万吨在f 2 = 61赫兹。 </li></ol><img alt="图1" src="/files/ftp_upload/53869/53869fig1.jpg" /> 图1的p FMMD的示意图设置两个测量头电连接到彼此。将样品放置在头之间的空间。检测线圈（+）测量样品信号，反卷绕检测线圈（ - ）作为参考，以从高频激磁线圈抵消直接字段。放大器 - 前置放大器，X - 混频器，低通滤波器 - 低通滤波器，DAQ - 数据采集。目标="_空白"&gt;点击此处查看该图的放大版本。 2.构建测量头<ol><li>构造的p FMMD使得连接上方和下方的样品两套激发和检测线圈。每一组线圈包括一个低频驱动器线圈，高频激磁线圈，以及包含在轴向梯度仪配置两个相对伤口拾取线圈的差动检测线圈。 <ol><li>为了允许至少一个激励线圈相对于所述差分检测线圈的调节，以便能够在高频激励的直接感应平衡到检测线圈。例如，安装在一个线程允许励磁线圈与检测线圈的相对运动的励磁线圈。在p FMMD的示意图示于图1; 图2示出了技术图纸和设置的照片。详细线圈的参数列于表1中 。 </li></ol></li><li>安装线圈组上方和上一个刚性支撑样品的下方，与同轴取向，参见图1和2。确保两个线圈组不振动相对于彼此。 </li><li>通过施加高频电流，从而相应激励线圈组，它们之间的不同的相对位置，同时在与检测线圈组这个频率测量所检测的信号，使用的设备，如调整测量头的高频平衡示波器或锁定放大器。 <ol><li>调整直接感应电压低至几毫伏， 即直接诱导超过1000倍的抑制。通过观察励磁电流和检测的电压之间的相移确定的可调节的限制。在最小，感应电压为90°相移作为比较d可直接诱导。 </li></ol></li></ol><img alt="图2" src="/files/ftp_upload/53869/53869fig2.jpg" /> 图2.技术图纸和p FMMD头部的照片。沿一垂直平面的横截面（左上）和一个水平面（左下）中示出以及线圈卷绕前的照片的开测量头的。 1 - 铝的支持，2 - 线圈前者用于检测线圈，3 - 螺纹线圈前者为励磁线圈，可上升/下跌的旋转，4 - 样品支撑板，5 - 铝盖，6 - 样塞的支持，7 - 止动件在x方向，8 -挡块在y方向上 。 6 - 8为扫描被除去。在p FMMD头的大小为77毫米×68毫米×29毫米。 <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/53869/53869fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 3.设置测量电子<ol><li>配置EXCI塔季翁部分，由两个振荡器和功率放大器为低频驱动器线圈和高频励磁线圈。 <ol><li>设置低频驱动器部分，包括振荡器和用于低频率f 2的功率放大器。计算放大器，使得它提供所需的电流以产生在驱动线圈5 mT的领域的力量。在这里，使用直接数字合成（DDS）芯片的可编程振荡器。采用高速缓冲作为功率放大器。 </li><li>设置高频激发部分，包括振荡器和用于高频率f 1的功率放大器。设置功率放大器，使得它提供所需的电流，以产生在励磁线圈约0.5 mT的领域。使用DDS芯片和一个高速缓冲分别作为振荡器和功率放大器。 </li></ol></li><li>配置检测部，包括一个preamplifie的R，第一混频器，以从高频率f 1，中间放大器和滤波器，一个第二混频器从两倍的低频2·解调f 2和最终的过滤器和输出驱动器解调。可替代地，使用两个锁定放大器来实现检测电子。 <ol><li>设置前置放大器级。选择输入运算放大器（OP），考虑到检测线圈和增益带宽积的阻抗。执行噪声优化过程，考虑到指定的电压噪声和OP的电流噪声，如在参考文献说明。 10.选择具有约100中的第一阶段的扩增高速低噪声运算放大器。后续阶段不是关键，但检查输出信号保持在电压范围内， 即，由于超载不失真。这里，使用具有4.3倍的放大的低噪声JFET输入运算放大器。 </li><li>设置在FIRST解调级中，以高频率f 1中的放大的信号相乘。使用模拟乘法器芯片，以实现对解调的可调相位从第二个独立的DDS芯片引用它。或者，使用锁定放大器作为前置放大器（3.2.1），第一解调器（3.2.2）和高频发生器（3.1.2）。 </li><li>设置在中间放大和滤波级。实现的低通滤波器，使得在2·f 2 的道次信号频率原状而在f 1和2· 女 1寄生高频成分被有效地抑制。通过用大约100总放大选择两个通用运算放大器选择合适的中间放大，例如。 </li><li>设置在第二解调级，滤波和放大的信号与低频率的两倍2·乘以f 2 的 。使用模拟乘法器芯片和从第四分开DDS芯片引用它，以实现用于解调一个可调相。可替代地，使用能够二次谐波解调作为中间放大器（3.2.3）中，在二次谐波（3.2.4）第二解调器和低频发生器（3.1.1）的一个锁定放大器。 </li><li>设置最终放大和滤波级。实现的低通滤波器，使得在扫描频率的信号频率通过原状，而在4寄生高频成分·f 2 的被有效地抑制。选择合适的最终放大，考虑到所需的输出电压范围。使用两个通用运算放大器约10共放大。 </li></ol></li></ol> 4.设置2D扫描仪<ol><li>装入2D扫描器，使得运动平面垂直于线圈的轴线。 </li><li>控制二维扫描仪和同步acquiri纳克为了获得使用写在编程语言的Python一个自制的脚本平面样品的FMMD信号的2D图像从测量电子输出电压。 </li></ol> 5.准备样品<ol><li>使用直径为50纳米至100纳米，磁赤铁矿颗粒磁铁矿颗粒的直径为1微米，其中浓度为25.0毫克/毫升。通过在水中的磁性粒子溶解，使用磁体将它们分开并丢弃水洗涤溶液。重复该过程三次。稀磁性粒子溶液到十分之一用蒸馏水。 </li><li>通过活检冲床冲孔吸收吸墨纸件准备用直径为2.0 mm纸张颗粒样品。浸泡其中在不同浓度的磁珠溶液30秒，并让他们在空气中干燥。这里，可使用的0.04，0.2，1，5和25毫克/毫升100纳米大小的颗粒的浓度。 </li><li>使用nitrocellulos制备样品尺寸个2.0毫米×18.0毫米ê膜。与未稀释的1微米直径的颗粒溶液浸泡该膜。准备由均匀浸泡膜一个样本，和另一个通过一个浓度梯度。通过浸泡在膜的端部在与不同浓度的珠粒溶液中，产生的浓度梯度（ 图5）执行此操作。 </li><li>制备于10μl体积的毛细管的样品，外径400微米，长40毫米。填充未稀释的50纳米直径的粒子溶液的毛细管。制备具有20倍稀释液的第二微管（1.9毫升水混合100微升未稀释溶液）。 </li></ol> 6.执行2D FMMD扫描<ol><li>根据平面尺寸A×B的样品的选择扫描区。在扫描软件输入值。 </li><li>选择步进方向。通常情况下，这两个平面尺寸的短，让我们把它叫做b </青霉&gt;，将被选择为，因为需要较少的步骤，从而减少加速和减速阶段的步进方向。 </li><li>选择扫描速度v，以考虑由于低通滤波信号还原，见讨论。调整的速度1和7毫米/秒之间的值。输入在扫描软件中的值。 </li><li>选择步进距离ΔB，考虑到它不必比实现的空间分辨率更小，总扫描时间t，这将是至少T = A / V·B /Δb +1）。输入在软件步进距离。 </li><li>安装在2D扫描仪的样本。修复它使用胶带塑料板。 </li></ol><img alt="图3" src="/files/ftp_upload/53869/53869fig3.jpg" /> 图3.对FMMD测量设置的照片。样品贴有塑料支架上的胶带由电机移动阶段（左）。然后将样品在p FMMD头（右）扫描。 <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/53869/53869fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <ol start="6"><li>按下启动按钮执行扫描。 图5和6盖20.0毫米（X轴）的×25.0毫米（y轴）区域，扫描即 ，六25mm长痕量沿y轴扫描，以在x方向4.0毫米步骤，在一个阶段的速度为1.0毫米/秒。这相当于约2分钟的扫描时间。 </li></ol><img alt="图4" src="/files/ftp_upload/53869/53869fig4.jpg" /> 图4.图形用户扫描软件的接口 ，扫描参数在此输入。测量是通过按下红色按钮启动。 7.图像处理<ol><li>使用homemad原始数据转换成矩阵形式在python脚本ë。在一个2列逗号分隔值（CSV）格式文件多余的值记录整个扫描的原始数据一起。额外的列指示踩踏动作期间捕获相应的数据。该脚本片段在额外的列值的每一个变化的原始数据列，并删除步进运动过程中的数据段。它也通过将剩余的连续段成矩阵的行或列构建所得矩阵和矩阵写入CSV格式文件。 注意:使用python脚本生成该研究对FMMD图像。的pyplot.contour函数和从matplotlib库蟒的pyplot.imshow功能累积地用于制备轮廓和背景颜色，分别。 </li></ol>

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The authors have nothing to disclose.

测量技术利用了超顺磁性粒子的磁化曲线的非线性。双面测量头同时施加不同频率的两个磁激励场的样品，一个低频率（f 2）成分以驱动颗粒进入磁饱和和高的频率（f 1）探测场来测量非线性磁响应。尤其，入射场的两个谐波， 男 · 女 1和n·f 2和总和的频率中，M· 女 1 + N·f 2 ?...

<html>磁性纳米颗粒（MNP）已发现在分子生物学和医学， 即广泛应用，用于生物分子的操纵和单电池1，用于选择性标记进行检测，2，3靶实体染色质调制，4和mRNA分离和癌症治疗5由于其超顺属性，它们是用于医疗成像特别有用。它们可以通过使用超导量子干涉仪（SQUID）检测服务，例如，如造影剂或示踪剂磁共振成像（MRI）或用于磁敏成像2,6的超顺磁性纳米颗粒，得到了良好的对比度，以人类的不同组织体，其是dia-或顺7因此，颗粒可以方便地用于获得人体部位具有相对良好的空间分辨率和灵敏度的医学图像。8 通过GLEICH和Weizenecker 9中引入帐篷"&gt;磁粉成像（MPI）技术利用粒子的磁化非线性的。在零或弱磁场偏差，MNP对频率f的交流激励的反应是强烈的，由于其大的易感性，尤其是粒子的非线性磁化引起谐波N·f的产生，其中n = 2，3，4 ...在高磁场偏置，谐波响应变弱，因为粒子被磁饱和，在在MPI技术中，样品完全除自由场线（FFL）或无场点（FFP）磁化。只有粒子靠近这条线或点将有助于样品的非线性响应。随着适当的接收器线圈的FFP和就业运动，GLEICH和Weizenecker获得MPI图片包含有1mm的空间分辨率。 为了获得MNP的空间分布的信息，这两种方法通常被使用的，传感器的相对于该样品，或FFL / FFP的运动由电磁铁装置2,3的机械运动在后一种情况下，图像重建技术像谐波空间MPI 3或X-空间MPI 10，11，12是必需的。 MPI的空间分辨率被激发和检测线圈的卷积特性以及由磁场梯度的特性来确定。这允许图像重建算​​法，以获得在原始分辨率，这是由拾取线圈的大小和距离以及由麦克斯韦方程支配的磁场分布确定的更高的分辨率。 一个MPI扫描器通常由强磁体用于磁化整个样本，以操纵跨越样品FFL或FFP可控线圈系统，高频激励下Ñ​​线圈系统，以及用于拾取来自样品的非线性响应的检测线圈系统。的FFL / FFP通过样品体积连续移动而从该不饱和样品区的谐波响应被记录。为了避免装配试样放入扫描仪的问题，一个单面MPI扫描器已由格拉夫等人 13表明，但是在降低性能为代价的。如果样品是由磁体和线圈包围得到最好的结果。因为样本具有除FFL / FFP区域充分磁化，该技术需要用水冷却相对大和强烈的磁铁，从而导致相当笨重的MPI系统。 我们的方法是基于频率在超顺磁性粒子的非线性磁化曲线混合14当超paramagnets以两个不同的频率（f1和f2 &lt;暴露于磁场/ EM&gt; 2），较线性组合·M·˚F和频1 + N·F 2（整数数m，生成N）。结果表明，这些组件的外观是高度特异性的粒子的磁化曲线的非线性。15换句话说，当MNP样品在频率f 2和频率的探测场同时暴露于一个驱动磁场F 1，将颗粒在频率f生成响应字段1 + 2·f 2 的 。无磁性非线性样品这个总和频率不会存在，因此特异性极高。我们称这种方法"混频磁性检测"（FMMD）。实验已经证实，该技术产生的颗粒浓度数量级大于四个数量的动态范围。14 &lt;P类="jove_content"&gt;相反典型MPI仪表，平面混频磁性检测（对- FMMD）方法不需要接近磁化样品到饱和，因为总和频率分量f的产生1 + 2· 女 图2是在零静态偏置字段最大14因此，需要有强烈的和笨重的磁体被减轻。事实上，该测量头的外部尺寸是仅77毫米×68毫米×29毫米。为了比较，MPI设置通常米尺寸7的缺点，但是，是该技术只限于平面样品以2mm的当前设置的最大厚度。样品必须被相对扫描到双面测量头。重新构造允许较厚的样品是可能的，但要在空间分辨率的损失进行交易。 在此基础上FMMD技术，我们提出了一个特殊类型的MPI的DETEC器为平面样品，即所谓的"平面混频磁性检测"（对 - FMMD）扫描仪。这一原则已被最近出版的17本工作中，我们专注于技术和目前的协议的方法，如何建立这样的扫描仪，以及如何执行扫描。它已经表明MPI可应用于医疗诊断目的，例如心血管或癌症成像。16，18，19因此，我们认为，新的MPI扫描器可用于广泛的潜在应用， 例如 ，用于测量磁性粒子分布组织切片。

<table><tbody><tr><td>Magnetic particles &quot;SiMAG Silanol&quot;</td><td>Chemicell (http://www.chemicell.com)</td><td>1101-5</td><td>Aqueous dispersion of magnetic silica particles, Maghemite, dia. 1&amp;nbsp;&amp;micro;m</td></tr><tr><td>Magnetic nanoparticles &quot;fluidMAG-Amine&quot;</td><td>Chemicell (http://www.chemicell.com)</td><td>4121-5</td><td>Aqueous dispersion of magnetic nanoparticles, Magnetite, dia. 50&amp;nbsp;nm</td></tr><tr><td>Microtube 10 &amp;micro;l</td><td>Hirschmann Laborger&amp;auml;te (http://www.hirschmann-laborgeraete.de/?sc_lang=en)</td><td></td><td>volume 10 &amp;micro;l, outer diameter 400&amp;nbsp;&amp;micro;m, length 40 mm</td></tr><tr><td>Nitrocellulose Membrane Biodyne B</td><td>Thermo Scientific (http://www.thermoscientific.com)</td><td>77016</td><td>Biodyne B Nylon Membrane, 0.45&amp;nbsp;&amp;micro;m, 8&amp;nbsp;cm x 12 cm</td></tr><tr><td>DDS chip AD9834</td><td>Analog Devices (http://www.analog.com)</td><td>AD9834</td><td>20 mW Power, 2.3 V to 5.5 V, 75&amp;nbsp;MHz Complete DDS</td></tr><tr><td>Operational Amplifier AD829</td><td>Analog Devices (http://www.analog.com)</td><td>AD829</td><td>High Speed, Low Noise Video Op Amp</td></tr><tr><td>Analog Multiplier MPY634</td><td>Texas Instruments (http://www.ti.com)</td><td>MPY634</td><td>Wide Bandwidth Precision Analog Multiplier</td></tr><tr><td>High-Speed Buffer BUF634</td><td>Texas Instruments (http://www.ti.com)</td><td>BUF634</td><td>250&amp;nbsp;mA High-Speed Buffer</td></tr><tr><td>Operational Amplifier OPA627</td><td>Texas Instruments (http://www.ti.com)</td><td>OPA627</td><td>Precision High-Speed Difet(R) Operational Amplifiers</td></tr><tr><td>Operational Amplifier TL072</td><td>Texas Instruments (http://www.ti.com)</td><td>TL072</td><td>Dual Low-Noise JFET-Input General-Purpose Operational Amplifier</td></tr><tr><td>Lock-In Amplifier SR830</td><td>Stanford Instruments (http://www.thinksrs.com)</td><td>SR830</td><td>100 kHz DSP lock-in amplifier</td></tr><tr><td>XYZ motorized stage</td><td>Sciencetown, Incheon, Korea (http://mkmsll.en.ec21.com/)</td><td></td><td></td></tr><tr><td>Cleanroom wiper</td><td>Seoul Semitech Co (http://www.seoulsemi.com)</td><td>CF-909</td><td>dimension 2.0 mm &amp;times; 18&amp;nbsp;mm</td></tr></tbody></table>

frequency mixing magnetic detection scanner for imaging magnetic particles in planar samples

平面混频执行扁平样品的磁粒子成像（MPI）磁探测（P-FMMD）扫描仪的设置提出。它由上安装在U形支撑件的腿的样本两侧的两个磁测量磁头。样品被局部暴露于由两个不同的频率，有更强的组分在约77千赫的磁激励场和一个较弱的磁场在61赫兹。超顺磁性粒子的非线性磁化特性引起的互调产物的产生。的高频和低频磁场入射到磁非线性颗粒的选定和频分量由解调电子记录。在对比常规的MPI扫描器，由于两个频率的混合发生在本地对 - FMMD不需要强磁场的整个样品中的应用。因此，样品的横向尺寸只是由扫描范围和支撑的限制。然而，样品的高度决定了空间分辨率。在当前的设置，是限定于2毫米。作为例子，我们提出从样品中硅醇基基质，并与氨基硅烷基50纳米磁性颗粒1微米直径的颗粒磁赤铁矿收购了两家20毫米×25毫米毫米P-FMMD图像。的结果表明，该新型的MPI扫描器可以应用于生物薄样品的分析和用于医疗诊断目的。

图5a示出的内双差分检测线圈的所计算出的灵敏度分布的坐标x的在样品平面的函数和y。它是通过确定在由所有四个检测线圈产生的中央平面中的所有点（X，Y）的磁场叠加在逆方法算出。相反，这个判断上述检测线圈对在每个这些点的磁矩灵敏度。计算被逼近线圈的高度可以忽略不计长的线圈进行。因此，在图5a中所示...

Watch this Scientific Journal Video about Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples at JoVE.com

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

一种用于成像平面样品中的磁性粒子扫描器用的是平面混频磁性检测技术的发展。从颗粒的非线性nonhysteretic磁化磁互调产物的反应后的两频率激励被记录。它可用于取薄的生物样品的二维图像。

混频磁探测仪在平面样品成像磁性微粒

The setup of a planar Frequency Mixing Magnetic Detection (p-FMMD) scanner for performing Magnetic Particles Imaging (MPI) of flat samples is presented. ...

frequency-mixing-magnetic-detection-scanner-for-imaging-magnetic

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

9.5K 次观看.  Electronics & Telecommunication Research Institute (ETRI). 一种用于成像平面样品中的磁性粒子扫描器用的是平面混频磁性检测技术的发展。从颗粒的非线性nonhysteretic磁化磁互调产物的反应后的两频率激励被记录。它可用于取薄的生物样品的二维图像。 

视频: Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

Registered Bioimaging of Nanomaterials for Diagnostic and Therapeutic Monitoring

Nanomedications can be carried by blood borne monocyte-macrophages into the reticuloendothelial system (RES; spleen, liver, lymph nodes) and to end organs. The latter include the lung, RES, and brain and are operative during human immunodeficiency virus type one (HIV-1) infection. Macrophage entry into tissues is notable in areas of active HIV-1 replication and sites of inflammation. In order to assess the potential of macrophages as nanocarriers, superparamagnetic iron-oxide and/or drug laden particles coated with surfactants were parenterally injected into HIV-1 encephalitic mice. This was done to quantitatively assess particle and drug biodistribution. Magnetic resonance imaging (MRI) test results were validated by histological coregistration and enhanced image processing. End organ disease as typified by altered brain histology were assessed by MRI. The demonstration of robust migration of nanoformulations into areas of focal encephalitis provides '"proof of concept" for the use of advanced bioimaging techniques to monitor macrophage migration. Importantly, histopathological aberrations in brain correlate with bioimaging parameters making the general utility of MRI in studies of cell distribution in disease feasible. We posit that using such methods can provide a real time index of disease burden and therapeutic efficacy with translational potential to humans.

Bioimaging methods used to assess cell biodistribution of nanoparticles are applicable for therapeutic and diagnostic monitoring of nanoformulated compounds. The methods described herein are sensitive and specific when assessed by histological coregistration. The methodologies provide a translational pathway from rodent to human applications.

注册生物成像，纳米材料可用于诊断和治疗监测

Nanomedications can be carried by blood borne monocyte-macrophages into the reticuloendothelial system (RES; spleen, liver, lymph nodes) and to end ...

科研

生物工程

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in these structures are held together by physical interactions mediated by a network of extracellular polymeric substances. Bacterial biofilms impact many human activities and the understanding of their properties is crucial for a better control of their development &#8212; maintenance or eradication &#8212; depending on their adverse or beneficial outcome. This paper describes a novel methodology aiming to measure in situ the local physical properties of the biofilm that had been, until now, examined only from a macroscopic and homogeneous material perspective. The experiment described here&#160;involves introducing magnetic particles into a growing biofilm to seed local probes that can be remotely actuated without disturbing the structural properties of the biofilm. Dedicated magnetic tweezers were developed to exert a defined force on each particle embedded in the biofilm. The setup is mounted on the stage of a microscope to enable the&#160;recording of time-lapse images of the particle-pulling period. The particle trajectories are then extracted from the pulling sequence and the local viscoelastic parameters are derived from each particle displacement curve, thereby providing the 3D-spatial distribution of the parameters. Gaining insights into the biofilm mechanical profile is essential from an engineer&#39;s point of view for biofilm control purposes but also from a fundamental perspective to clarify the relationship between the architectural properties and the specific biology of these structures.

Remote Magnetic Actuation of Micrometric Probes for in situ 3D Mapping of Bacterial Biofilm Physical Properties

This paper shows an original methodology based on the remote actuation of magnetic particles seeded in a bacterial biofilm and the development of dedicated magnetic tweezers to measure in situ the local mechanical properties of the complex living material built by micro-organisms at interfaces.

测微探针进行远程磁驱动<em&gt;原位</em&gt; 3D细菌生物膜物理性质的映射

Bacterial adhesion and growth on interfaces lead to the formation of three-dimensional heterogeneous structures so-called biofilms. The cells dwelling in ...

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan electron-paramagnetic-resonance (RS-EPR), which can provide quantitative information under in vivo conditions on oxygen concentration, pH, redox status and concentration of signaling molecules (i.e., OH&#8226;, NO&#8226;). The RS-EPR technique has a higher sensitivity, improved spatial resolution (1 mm), and shorter acquisition time in comparison to the standard continuous wave (CW) technique. A variety of phantom configurations have been tested, with spatial resolution varying from 1 to 6 mm, and spectral width of the reporter molecules ranging from 16 &#181;T (160 mG) to 5 mT (50 G). A cross-loop bimodal resonator decouples excitation and detection, reducing the noise, while the rapid scan effect allows more power to be input to the spin system before saturation, increasing the EPR signal. This leads to a substantially higher signal-to-noise ratio than in conventional CW EPR experiments.

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

A new electron paramagnetic resonance (EPR) method, rapid scan EPR (RS-EPR), is demonstrated for 2D spectral spatial imaging which is superior to the traditional continuous wave (CW) technique and opens new venues for in vivo imaging. Results are demonstrated at 250 MHz, but the technique is applicable at any frequency.

快速扫描电子顺磁共振打开新的途径成像生理重要参数<em&gt;在体内</em

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan ...

Magnetic Field Mapping using Off-Axis Electron Holography in the Transmission Electron Microscope

Off-axis electron holography is a powerful technique that involves the formation of an interference pattern in a transmission electron microscope (TEM) by overlapping two parts of an electron wave, one of which has passed through a region of interest on a specimen and the other is a reference wave. The resulting off-axis electron hologram can be analyzed digitally to recover the phase difference between the two parts of the electron wave, which can then be interpreted to provide quantitative information about local variations in electrostatic potential and magnetic induction within and around the specimen. Off-axis electron holograms can be recorded while a specimen is subjected to external stimuli such as elevated or reduced temperature, voltage, or light. The protocol that is presented here describes the practical steps that are required to record, analyze, and interpret off-axis electron holograms, with a primary focus on the measurement of magnetic fields within and around nanoscale materials and devices. Presented here are the steps involved in the recording, analysis, and processing of off-axis electron holograms, as well as the reconstruction and interpretation of phase images and visualization of the results. Also discussed are the need for optimization of the specimen geometry, the electron optical configuration of the microscope, and the electron hologram acquisition parameters, as well as the need for the use of information from multiple holograms to extract the desired magnetic contributions from the recorded signal. The steps are illustrated through a study of specimens of B20-type FeGe, which contain magnetic skyrmions and were prepared with focused ion beams (FIBs). Prospects for the future development of the technique are discussed.

Guidelines are presented for recording and interpreting off-axis electron holograms to provide quantitative images of magnetic fields in nanoscale materials and devices in the transmission electron microscope.

Off-axis electron holography is a powerful technique that involves the formation of an interference pattern in a transmission electron microscope (TEM) by ...

工程学

High-Temperature and High-Pressure In situ Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy represents an important technique to understand the structure and bonding environments of molecules. There exists a drive to characterize materials under conditions relevant to the chemical process of interest. To address this, in situ high-temperature, high-pressure MAS NMR methods have been developed to enable the observation of chemical interactions over a range of pressures (vacuum to several hundred bar) and temperatures (well below 0 &#176;C to 250 &#176;C). Further, the chemical identity of the samples can be comprised of solids, liquids, and gases or mixtures of the three. The method incorporates all-zirconia NMR rotors (sample holder for MAS NMR) which can be sealed using a threaded cap to compress an O-ring. This rotor exhibits great chemical resistance, temperature compatibility, low NMR background, and can withstand high pressures. These combined factors enable it to be utilized in a wide range of system combinations, which in turn permit its use in diverse fields as carbon sequestration, catalysis, material science, geochemistry, and biology. The flexibility of this technique makes it an attractive option for scientists from numerous disciplines.

The molecular structures and dynamics of solids, liquids, gases, and mixtures are of critical interest to diverse scientific fields. High-temperature, high-pressure in situ MAS NMR enables detection of the chemical environment of constituents in mixed phase systems under tightly controlled chemical environments.

高温高压原位魔角旋转核磁共振光谱

Nuclear magnetic resonance (NMR) spectroscopy represents an important technique to understand the structure and bonding environments of molecules. There ...

化学

Magnetic Levitation Coupled with Portable Imaging and Analysis for Disease Diagnostics

Currently, many clinical diagnostic procedures are complex, costly, inefficient, and inaccessible to a large population in the world. The requirements for specialized equipment and trained personnel require that many diagnostic tests be performed at remote, centralized clinical laboratories. Magnetic levitation is a simple yet powerful technique and can be applied to levitate cells, which are suspended in a paramagnetic solution and placed in a magnetic field, at a position determined by equilibrium between a magnetic force and a buoyancy force. Here, we present a versatile platform technology designed for point-of-care diagnostics which uses magnetic levitation coupled to microscopic imaging and automated analysis to determine the density distribution of a patient's cells as a useful diagnostic indicator. We present two platforms operating on this principle: (i) a smartphone-compatible version of the technology, where the built-in smartphone camera is used to image cells in the magnetic field and a smartphone application processes the images and to measures the density distribution of the cells and (ii) a self-contained version where a camera board is used to capture images and an embedded processing unit with attached thin-film-transistor (TFT) screen measures and displays the results. Demonstrated applications include: (i) measuring the altered distribution of a cell population with a disease phenotype compared to a healthy phenotype, which is applied to sickle cell disease diagnosis, and (ii) separation of different cell types based on their characteristic densities, which is applied to separate white blood cells from red blood cells for white blood cell cytometry. These applications, as well as future extensions of the essential density-based measurements enabled by this portable, user-friendly platform technology, will significantly enhance disease diagnostic capabilities at the point of care.

We present a magnetic levitation technique coupled with automated imaging and analysis in both a smartphone-compatible device and a device with embedded imaging and processing. This is applied to measure the density distribution of cells with two demonstrated biomedical applications: sickle cell disease diagnosis and separating white and red blood cells.

磁悬浮加上便携式成像与分析诊断疾病

Currently, many clinical diagnostic procedures are complex, costly, inefficient, and inaccessible to a large population in the world. The requirements for ...

Rapid Homogeneous Detection of Biological Assays Using Magnetic Modulation Biosensing System

A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or separation step. When the IL-8 target was present, a 'sandwich'-based assay attached magnetic beads with IL-8 capture antibody to streptavidin coupled fluorescent protein via the IL-8 target and a biotinylated IL-8 antibody. The magnetic beads are maneuvered into oscillatory motion by applying an alternating magnetic field gradient through two electromagnetic poles. The fluorescent proteins, which are attached to the magnetic beads are condensed into the detection area and their movement in and out of an orthogonal laser beam produces a periodic fluorescent signal that is demodulated using synchronous detection. The magnetic modulation biosensing system was previously used to detect the coding sequences of the non-structural Ibaraki virus protein 3 (NS3) complementary DNA (cDNA) [2]. The techniques that are demonstrated in this work for external manipulation and condensation of particles may be used for other applications, e.g. delivery of magnetically-coupled drugs in-vivo or enhancing the contrast for in-vivo imaging applications.

Magnetic modulation biosensing system is utilized to rapidly, sensitively and simply detect biological assays, such as DNA molecules and proteins.

利用磁调制生物传感系统的生物检测的快速均质检测

A magnetic modulation biosensing system (MMB) [1,2] rapidly and homogeneously detected biological targets at low concentrations without any washing or ...

生物学

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force microscopy (AFM) probe whose tip has been magnetized vertically (i.e., perpendicular to the probe cantilever) is oscillated at a fixed height above the sample surface. The resultant shifts in the oscillation phase or frequency, which are proportional to the magnitude and sign of the vertical magnetic force gradient at each pixel location, are then tracked and mapped. Although the spatial resolution and sensitivity of the technique increases with decreasing lift height above the surface, this seemingly straightforward path to improved MFM images is complicated by considerations such as minimizing topographical artifacts due to shorter range van der Waals forces, increasing the oscillation amplitude to further improve sensitivity, and the presence of surface contaminants (in particular water due to humidity under ambient conditions). In addition, due to the orientation of the probe's magnetic dipole moment, MFM is intrinsically more sensitive to samples with an out-of-plane magnetization vector. Here, high-resolution topographical and magnetic phase images of single and bicomponent nanomagnet artificial spin-ice (ASI) arrays obtained in an inert (argon) atmosphere glovebox with &lt;0.1 ppm O2 and H2O are reported. Optimization of lift height and drive amplitude for high resolution and sensitivity while simultaneously avoiding the introduction of topographical artifacts is discussed, and detection of the stray magnetic fields emanating from either end of the nanoscale bar magnets (~250 nm long and &lt;100 nm wide) aligned in the plane of the ASI sample surface is shown. Likewise, using the example of a Ni-Mn-Ga magnetic shape memory alloy (MSMA), MFM is demonstrated in an inert atmosphere with magnetic phase sensitivity capable of resolving a series of adjacent magnetic domains each ~200 nm wide.

Magnetic force microscopy (MFM) employs a vertically magnetized atomic force microscopy probe to measure sample topography and local magnetic field strength with nanoscale resolution. Optimizing MFM spatial resolution and sensitivity requires balancing decreasing lift height against increasing drive (oscillation) amplitude, and benefits from operating in an inert atmosphere glovebox.

优化磁力显微镜分辨率和灵敏度，以可视化纳米级磁畴

Magnetic force microscopy (MFM) enables mapping local magnetic fields across a sample surface with nanoscale resolution. To perform MFM, an atomic force ...

Quantifying Mixing using Magnetic Resonance Imaging

Mixing is a unit operation that combines two or more components into a homogeneous mixture. This work involves mixing two viscous liquid streams using an in-line static mixer. The mixer is a split-and-recombine design that employs shear and extensional flow to increase the interfacial contact between the components. A prototype split-and-recombine (SAR) mixer was constructed by aligning a series of thin laser-cut Poly (methyl methacrylate) (PMMA) plates held in place in a PVC pipe. Mixing in this device is illustrated in the photograph in Fig. 1. Red dye was added to a portion of the test fluid and used as the minor component being mixed into the major (undyed) component. At the inlet of the mixer, the injected layer of tracer fluid is split into two layers as it flows through the mixing section. On each subsequent mixing section, the number of horizontal layers is duplicated. Ultimately, the single stream of dye is uniformly dispersed throughout the cross section of the device.
 Using a non-Newtonian test fluid of 0.2% Carbopol and a doped tracer fluid of similar composition, mixing in the unit is visualized using magnetic resonance imaging (MRI). MRI is a very powerful experimental probe of molecular chemical and physical environment as well as sample structure on the length scales from microns to centimeters. This sensitivity has resulted in broad application of these techniques to characterize physical, chemical and/or biological properties of materials ranging from humans to foods to porous media 1, 2. The equipment and conditions used here are suitable for imaging liquids containing substantial amounts of NMR mobile 1H such as ordinary water and organic liquids including oils. Traditionally MRI has utilized super conducting magnets which are not suitable for industrial environments and not portable within a laboratory (Fig. 2). Recent advances in magnet technology have permitted the construction of large volume industrially compatible magnets suitable for imaging process flows. Here, MRI provides spatially resolved component concentrations at different axial locations during the mixing process. This work documents real-time mixing of highly viscous fluids via distributive mixing with an application to personal care products.

Magnetic resonance imaging (MRI) provides a powerful tool to evaluate the effectiveness of process equipment during operation. We discuss the use of MRI to visualize mixing in a static mixer. The application is relevant to personal care products, but can be applied to a broad range of food, chemical, biomass and biological fluids.

量化混合使用磁共振成像

Mixing is a unit operation that combines two or more components into a homogeneous mixture.  This work involves mixing two viscous liquid streams using an ...

Fabrication of Magnetic Platforms for Micron-Scale Organization of Interconnected Neurons

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. Many studies have aimed at directing neurons using chemical and topographical cues. However, reports of organizational control on a micron-scale over large areas are scarce. Here, an effective method has been described for placing neurons in preset sites and guiding neuronal outgrowth with micron-scale resolution, using magnetic platforms embedded with micro-patterned, magnetic elements. It has been demonstrated that loading neurons with magnetic nanoparticles (MNPs) converts them into sensitive magnetic units that can be influenced by magnetic gradients. Following this approach, a unique magnetic platform has been fabricated on which PC12 cells, a common neuron-like model, were plated and loaded with superparamagnetic nanoparticles. Thin films of ferromagnetic (FM) multilayers with stable perpendicular magnetization were deposited to provide effective attraction forces toward the magnetic patterns. These MNP-loaded PC12 cells, plated and differentiated atop the magnetic platforms, were preferentially attached to the magnetic patterns, and the neurite outgrowth was well aligned with the pattern shape, forming oriented networks. Quantitative characterization methods of the magnetic properties, cellular MNP uptake, cell viability, and statistical analysis of the results are presented. This approach enables the control of neural network formation and improves neuron-to-electrode interface through the manipulation of magnetic forces, which can be an effective tool for in vitro studies of networks and may offer novel therapeutic biointerfacing directions.

This work presents a bottom-up approach to the engineering of local magnetic forces for control of neuronal organization. Neuron-like cells loaded with magnetic nanoparticles (MNPs) are plated atop and controlled by a micro-patterned platform with perpendicular magnetization. Also described are magnetic characterization, MNP cellular uptake, cell viability, and statistical analysis.

为互连神经元微缩组织制造磁平台

The ability to direct neurons into organized neural networks has great implications for regenerative medicine, tissue engineering, and bio-interfacing. ...

混频磁探测仪在平面样品成像磁性微粒

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