Motile sample handling and tracking during magnetic resonance microscopy

Abstract: The nematode Caenorhabditis elegans (C. elegans) is a model organism that has been used in a wide spectrum of biological investigations, including genetics, cell biology and neurobiology. The potential usefulness of C. elegans stems from a balance between biological simplicity and complexity, allowing one to address high-level biological questions and provide a unique opportunity to model human ailments, such as Alzheimer’s and Parkinson’s disease. However, assigning functions to every gene in a living organism is the next challenge for functional genomics. It is estimated that 85 – 90 % of the ca. 19,000 genes of the nematode genome do not produce a visible phenotype when deactivated, which hampers determining their function, especially when they do not belong to previously characterized gene families. Therefore, a window to the metabolic responses that result from such deactivations is highly desirable.

Nuclear magnetic resonance (NMR) spectroscopy is one of the most information-rich methods, which provided a unique opportunity to link morphological, functional and chemically specific spectroscopic information from small volume (e.g., μL) samples. Because the technology is non-invasive and only non-ionizing radiation is absorbed and emitted, it is especially suitable for the in vivo study of C. elegans. However, motility of this small model organism poses a key challenge for the in vivo acquisition of magnetic resonance signals. A key element for the reduction of motion artefacts is the availability of a motion capture system that is operated simultaneously with the NMR experiment. Microfabrication techniques hold potential to yield intelligent probe and fluidic system in combination with detection methods to achieve highly parallel NMR signal acquisition, which together could deliver unprecedented structural and quantitative information from complex samples. A miniature highly integrated platform coupled with NMR detectors and microfluidics is promising to propel systematic study of C. elegans physiology, neurobiology and metabolomics on an individual basis for population of thousands of worms under normal physiological conditions.

In this PhD project, a necessary infrastructure for precise handling and tracking of C. elegans on demand has been presented, which has a potential to address the need for comprehensive NMR-driven analyses. Real-time positional sensing is accomplished by two methods: electrically and optically. First, a modular multifunctional platform for electrical position sensing over long periods of time, which performance was synchronized with the remaining functions of the NMR experiment, has been developed. The concept of the electrical impedance spectroscopy has been integrated into the microfluidic channel and extended with specifically designed sensing elements. To achieve this, several novel ionic liquid  polymer composites have been developed, which are amenable to two-photon polymerization (2-PP) nanolithography. This technology permitted precise single-step 3D manufacturing of high resolution (down to 150 nm) structures with excellent optical characteristics and electrical characteristics. As a result, enhanced detection sensitivity (up to 40 %), if compared to standard planar electrodes, without blocking optical visibility has been achieved. Immobilization of C. elegans has been accomplished mechanically by a narrowing of a microfluidic channel. Secondly, the necessary hardware and software are introduced to both capture the motion, extract the instantaneous velocity field at sufficient frame rates and extrapolate the velocity for a sufficient number of frames ahead so as to prospectively predict the future position of a nematode prospective NMR. A computational tool offered a powerful novel way to investigate the biological processes of freely moving sub-millimeter objects. In addition, a camera-based system has been validated to operate while immersed in a high magnetic field (11.7 Tesla)

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2018

Classification and Topics

• Classification: Biowissenschaften, Biologie
• Keyword: NMR-Spektroskopie ; Caenorhabditis elegans ; Mikrofluidik ; Zwei-Photonen-Polymerisation

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2018
• Creator: Bakhtina, Natalia A.
• Contributor: Korvink, Jan G. ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Further information

• DOI: 10.6094/UNIFR/15499
• URN: urn:nbn:de:bsz:25-freidok-154992
• Rights: Kein Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:41 PM CET