Diamond NMR spectrometer for microfluidic metabolite profiling

Project Summary. Nuclear magnetic resonance (NMR) is among the most powerful analytical techniques ever invented, as recognized by 6 Nobel Prizes for methods development alone. Nonetheless, NMR is notoriously plagued by poor sensitivity. State-of-the-art NMR spectrometers feature detection thresholds of ~5 nanomoles for µL sample volumes (~100 nanograms). This places NMR sensitivity many orders of magnitude behind other analytical chemistry techniques such as mass spectrometry, Raman spectroscopy, and fluorescence labeling. Improvements in NMR often focus on using larger magnets, but progress has plateaued; over the last 30 years, the fundamental signal strength has only increased ~2-fold. We seek to fundamentally change the NMR hardware by using diamond films doped with Nitrogen-Vacancy centers to detect nuclear magnetization non-inductively via pulsed optically detected magnetic resonance methods. The form factor of our NMR detector is easily integrated with hyphenation techniques so that samples can be separated into sub-components before analysis. In Phase I, we improved the sensitivity of diamond quantum sensors to the femtotesla level and identified microwave protocols suitable for high field operation. We built a tabletop microfluidic diamond NMR apparatus with 40 pL detection volume and used it for proof-of-principle NMR analytical chemistry experiments. In Phase II, we will optimize sensor spectral resolution and sensitivity, miniaturize the setup into a benchtop device, and validate its operation using metabolite mixtures. Afterwards, we will deliver our devices to end-users in industry (Merck) and academia (UW) and incorporate feedback to scale up to market. If successful, our prototype could have a profound impact on analytic biochemistry research, by combining mass-spectrometry-level sensitivity with NMR-level accuracy. Specifically, we improve upon existing analytical methods by offering: 1. Greater performance. We offer 1000-fold better sensitivity (picomole instead of nanomole) than current NMR spectrometers. This sensitivity approaches that of mass spectrometry but retains benefits of NMR such as non-destructive, absolute quantitation and structural identification. 2. Compatibility with hyphenated separation techniques. Our spectrometer is compact and easily integrated into microfluidic chips with online high-performance liquid chromatography-based assays (HPLC) for sample-limited analyses (metabolomics, pharmacodynamics, natural products). 3. Low cost. The small sample volume in our spectrometer leads to reduced engineering costs, resulting in greater affordability compared to current high-end NMR spectrometers.