Modular, low-cost point-of-care system for metabolomics applications

Tajabadi, Ataollah Mohammad Ali Abdullah Saleh (2025) Modular, low-cost point-of-care system for metabolomics applications. PhD thesis, University of Glasgow.

Abstract

This thesis presents the design, development, and validation of a modular, low-cost NMR system tailored for point-of-care diagnostics, with an emphasis on enabling early detection of prostate cancer. This application imposes specific requirements on the system, including the ability to detect low-concentration metabolic biomarkers in microlitre-scale biological fluids, maintain a compact footprint suitable for bedside or outpatient use, and deliver sufficient sensitivity despite the limitations of low-field operation. To meet these needs, two high sensitivity NMR probes were developed, each incorporating Lenz lenses to focus magnetic flux and enhance signal detection. The system architecture was designed for compatibility with small-volume samples and scalability for integration into portable diagnostic platforms.

The first probe iteration demonstrated a 40.6-fold increase in received power, confirming the effectiveness of Lenz lenses in amplifying local magnetic fields. However, alignment and robustness issues led to a second iteration optimised for field uniformity, achieving a 3.8-fold improvement while maintaining return losses below −10 dB at 28.566 MHz. Experimental validation confirmed impedance accuracy, with minor deviations highlighting component sensitivity.

Supporting NMR electronics were developed and characterised for efficient signal generation, amplification, and detection. A modular approach ensured accessibility, with impedance matching circuits validated via Smith charts and Monte Carlo simulations, maintaining return losses below −10 dB across 28–29.2 MHz. The system amplified signals down to 45 nV with a 12 dB signal-to-noise ratio (SNR), achieving a spin sensitivity of 5.07×1015 spins/ √Hz and a concentration sensitivity of 4.77 M/√Hz. Free induction decay signals were acquired, distinguishing water and oil based on transverse relaxation, with T∗2values of 0.489 ms and 0.412ms, respectively. Broad linewidths indicated magnetic field inhomogeneities requiring further refinement.

Compared to other low-cost NMR systems, this design offers improved energy efficiency and a modular architecture that supports customisation for a range of diagnostic applications. While this work is not yet suitable for metabolomics or clinical use in prostate cancer detection, it lays important groundwork for future development. The system demonstrates how high sensitivity can be achieved using microlitre-scale samples in a compact, low-cost platform, and its flexible design can be adapted to accommodate other sample formats or integrated into larger diagnostic workflows. With further advancements in spectral resolution, stability, and signal-to-noise performance, this platform has the potential to evolve into a practical point-of-care tool for early disease detection and biochemical analysis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Abbas, Dr. Hasan and Vellaisamy, Professor Roy
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85290
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 03 Jul 2025 10:26
• Last Modified: 03 Jul 2025 10:29
• Thesis DOI: 10.5525/gla.thesis.85290
• URI: https://theses.gla.ac.uk/id/eprint/85290

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