Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips.
Heteronuclear Micro-Helmholtz Coil Facilitates µm-Range Spatial and Sub-Hz Spectral Resolution NMR of nL-Volume Samples on Customisable Microfluidic Chips.
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DOI：
10.1371/journal.pone.0146384
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Korvink JG
中科院分区：
文献类型：
--
作者：
Spengler N;Höfflin J;Moazenzadeh A;Mager D;MacKinnon N;Badilita V;Wallrabe U;Korvink JG
我们提出了一种完全改进的模块化微核磁共振检测器，具有活性样品体积约100 nL，探针效率提高了87%。该检测器能够使用可交换的、特定应用的、mems制造的微流体样品容器快速筛选不同的样品。与我们之前的设计相反，样品支架芯片可以简单地用胶带密封，由于流体端口周围的光滑表面具有出色的附附性，因此可以承受~ 2.5 bar的压力，同时由于其优化的几何形状，可以实现高达0.62 Hz的H2O高光谱分辨率。我们还重新设计了线圈的设计和制造过程，用干胶片代替液体光刻胶，其最终厚度不依赖于精确的体积分配或固化过程中的精确平整。我们进一步引入了机械校准结构，以避免在组装过程中对芯片堆栈进行耗时的光学校准，同时我们将激光切割的PMMA间隔片替换为切块玻璃间隔片，这些间隔片在切割过程中不易熔化。这样做导致了整个制造链的整体简化，同时增加了产量，因为单个层厚度的均匀性得到了改善，此外，由于线键线圈的垂直定位更精确，现在由后基座平台划分。我们通过获得溶解在D2O中的~ 11 nmol蔗糖的1H谱来证明该设计的能力，其中我们实现了TSP参考峰的线宽为1.25 Hz。化学位移成像实验进一步记录了仅为~ 1.5 nl的体素体积，对应于1 M浓度下每体素仅1.5 nmol的量。为了将微探测器扩展到其他感兴趣的原子核，我们实现了一个陷阱电路，实现了异核光谱，并通过两个1H/13C 2D HSQC实验进行了验证。
We present a completely revised generation of a modular micro-NMR detector, featuring an active sample volume of ∼ 100 nL, and an improvement of 87% in probe efficiency. The detector is capable of rapidly screening different samples using exchangeable, application-specific, MEMS-fabricated, microfluidic sample containers. In contrast to our previous design, the sample holder chips can be simply sealed with adhesive tape, with excellent adhesion due to the smooth surfaces surrounding the fluidic ports, and so withstand pressures of ∼2.5 bar, while simultaneously enabling high spectral resolution up to 0.62 Hz for H2O, due to its optimised geometry. We have additionally reworked the coil design and fabrication processes, replacing liquid photoresists by dry film stock, whose final thickness does not depend on accurate volume dispensing or precise levelling during curing. We further introduced mechanical alignment structures to avoid time-intensive optical alignment of the chip stacks during assembly, while we exchanged the laser-cut, PMMA spacers by diced glass spacers, which are not susceptible to melting during cutting. Doing so led to an overall simplification of the entire fabrication chain, while simultaneously increasing the yield, due to an improved uniformity of thickness of the individual layers, and in addition, due to more accurate vertical positioning of the wirebonded coils, now delimited by a post base plateau. We demonstrate the capability of the design by acquiring a 1H spectrum of ∼ 11 nmol sucrose dissolved in D2O, where we achieved a linewidth of 1.25 Hz for the TSP reference peak. Chemical shift imaging experiments were further recorded from voxel volumes of only ∼ 1.5nL, which corresponded to amounts of just 1.5 nmol per voxel for a 1 M concentration. To extend the micro-detector to other nuclei of interest, we have implemented a trap circuit, enabling heteronuclear spectroscopy, demonstrated by two 1H/13C 2D HSQC experiments.