Abhyankar Nandita, Catterton Megan A, Cooksey Gregory A, Szalai Veronika A
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, United States.
National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
Anal Chem. 2024 Oct 29;96(43):17071-17077. doi: 10.1021/acs.analchem.4c00464. Epub 2024 Oct 15.
Planar or chip microresonators decrease the sample volume required for magnetic resonance spectroscopies to the nanoliter scale. However, the interrogation of nanoliter-scale solution samples on planar sensors is hindered by the lack of microfluidic devices that can simultaneously provide a small total volume and long-term sample stability. Here, we report microfluidic devices that decrease the total required sample volume to the submicroliter scale and also provide long-term physical stability and storability. We also report a 3D-printed microfluidic with a self-contained actuation mechanism, which allows the sample to be retracted from the microresonator surface for storage. The microfluidic devices are fabricated easily by laser cutting or 3D printing and are integrable with a broad range of planar sensors. We use planar inverse anapole (PIA) microresonators to obtain continuous wave (CW) electron paramagnetic resonance (EPR) spectra of natural-isotopic-abundance nitroxide radicals, which are ubiquitously used as reporters of biomolecular dynamics. We provide experimental evidence for a concentration sensitivity of 330 ± 40 nmol L, a concentration sensitivity limit of 800 ± 100 nmol L/mT√Hz, and an active volume no greater than 30 nL. Together, these developments represent an advance not only in the sensitivity of EPR spectroscopy but also in the design of microfluidics for stable, dead-volume-free placement of nanoliter-scale volumes of solutions on planar sensors.
平面或芯片微谐振器将磁共振光谱所需的样品体积减小到纳升尺度。然而，由于缺乏能够同时提供小总体积和长期样品稳定性的微流控装置，在平面传感器上对纳升尺度的溶液样品进行检测受到了阻碍。在此，我们报道了一种微流控装置，它将所需的总样品体积减小到亚微升尺度，并且还提供长期的物理稳定性和可存储性。我们还报道了一种具有自包含驱动机制的3D打印微流控装置，它可以将样品从微谐振器表面缩回以进行存储。这种微流控装置通过激光切割或3D打印很容易制造，并且可以与多种平面传感器集成。我们使用平面逆反极子（PIA）微谐振器来获取天然同位素丰度的氮氧化物自由基的连续波（CW）电子顺磁共振（EPR）光谱，氮氧化物自由基被广泛用作生物分子动力学的报告分子。我们提供了实验证据，表明其浓度灵敏度为330±40 nmol/L，浓度灵敏度极限为800±100 nmol/(L·mT√Hz)，有效体积不大于30 nL。这些进展共同代表了不仅在EPR光谱灵敏度方面，而且在用于在平面传感器上稳定、无死体积地放置纳升尺度溶液的微流控设计方面的进步。
