Nuclear Magnetic Resonance

Properties of Microcapsules

In collaboration with Dr. Patrick Degen and Prof. Dr. Heinz Rehage, Department of Chemistry

We investigate the properties of microcapsules consisting of calcium-alginate and have a diameter of about 1mm. Alginate, which is abundant in the cell walls of brown algae, is a copolymer of the saccharides mannuronate and guluronate. In the presence of divalent cations like calcium it forms stable membranes. These capsules can be used for transporting drugs with food. Hence it is important to study the diffusional processes through the membrane. For this purpose, we use pulsed-field gradient NMR and diffusion-weighted MRI at 600 MHz. Another property of interest is the thickness of the capsule membrane. This property can be investigated by spectroscopic imaging and NMR microscopy. The picture on the right shows an NMR-image of a composite capsule. The inner layer consists of pectinate, the outer layer of shellac.

MR-Imaging of flow in human blood vessel models

Fabian Keßelmann in collaboration with Dr. Frank Weichert, Department of Computer Science

MR Flow Imaging is a powerful tool for noninvasively measuring flow patterns, as well as in vivo and in vitro applications. It offers different methods to precisely measure directions of the flow, acceleration effects and velocity or to just visualize areas of moving spins. We are interested in the detailed flow behavior of liquids, especially blood, flowing through models of different complexity which simulate human blood vessels. Our 14 Tesla MR imaging system allows us to characterize flow on microscopic scales with resolutions that are much higher compared to common clinical MRI systems. The image on the right shows results of a simple four dimensional phase contrast MR flow measurement, which provides information of the velocity and the direction of flowing water molecules in a system consisting of two twisted silicon tubes.

Additional details of MR-Imaging of flow in human blood vessel models

Optimized selective excitation of metabolite signals

MR-spectroscopy allows the non-invasive detection of metabolite signals under in-vivo conditions. The concentration of some key metabolites contains important information about critical health conditions. In many cases, selective excitation is necessary to distinguish between overlapping signals and ensure a correct quantification of the target metabolite. Multiple quantum filter sequences can be used to filter signals from molecules with specific coupling patterns. We investigate their performance under non-ideal experimental conditions that are typical for standard clinical MRI scanners. Reliable and robust excitation techniques can be achieved through the optimization of RF-pulses on the basis of optimal control theory. The optimized sequences allow for an improved excitation of the desired metabolite and at the same time effective suppression of unwanted signals. The picture on the right shows an example system where lactate should be excited and alanine should be suppressed.

Relevant Publications:

[1] Synthesis and Molecular Structure of a Tricyclic Stannasiloxane Containing a Novel SiSn3O3F2 Structural Motif
J. Beckmann, K. Jurkschat, M. Schuermann, D. Suter and R. Willem|
Organometallics 21, 3819-3822 (2002)

[2] Adding salt to an aqueous solution of t-butanol: Is hydrophobic association enhanced or reduced?
D. Paschek, A. Geiger, M. J. Herve and D. Suter
J. Chem. Phys. 124, 154508 (2006)

[3] Effect of different sodium halides on the self-association of tertiary butanol in water
H. M. Jeufack and D. Suter
J. Chem. Phys. 126, 144501 (2007)

[4] Effect of cholesterol on diffusion in surfactant bilayers
T. Pieper, S. Markova, M. Kinjo and D. Suter
J. Chem. Phys. 127, 165102 (2007)

[5] Microslot NMR Probe for Metabolomics Studies
H. G. Krojanski, J. Lambert, Y. Gerikalan, D. Suter and R. Hergenröder
Analytical Chemistry 80, 8668-8672 (2008)

[6] Probing Liquid-Liquid Interfaces with Spatially Resolved NMR Spectroscopy
J. Lambert, R. Hergenröder, D. Suter and V. Deckert
Angewandte Chemie International Edition 48, 6343-6345 (2009)

[7] Deformation of liquid-filled calcium alginate capsules in a spinning drop apparatus
S. Leick, S. Henning, P. Degen, D. Suter and H. Rehage
Physical Chemistry Chemical Physics 12, 2950--2958 (2010)

[8] Liquid-State NMR Quantum Computing
L. M. K. Vandersypen, I. L. Chuang and D. Suter
Editors: D. M. Grant and R. K. Harris
John Wiley & Sons, Chichester (2010)

[9] Mechanical properties of liquid-filled shellac composite capsules
S. Leick, M. Kott, P. Degen, S. Henning, T. Pasler, D. Suter and H. Rehage
Phys. Chem. Chem. Phys. 13, 2765-2773 (2011)

[10] Sealing liquid-filled pectinate capsules with a shellac coating
S. Henning, S. Leick, M. Kott, H. Rehage and D. Suter
J. Microencapsulation 29, 147-155 (2012)

[11] Optically Enhanced Magnetic Resonance
D. Suter
Editors: R. K. Harris and R. Wasylishen
John Wiley & Sons, Chichester (2012)

[12] Characterizing permeability and stability of microcapsules for controlled drug delivery by dynamic NMR microscopy
S. Henning, D. Edelhoff, B. Ernst, S. Leick, H. Rehage and D. Suter
J. Magn. Reson. 221, 11 - 18 (2012)

[13] High-resolution MRI velocimetry compared with numerical simulations
D. Edelhoff, L. Walczak, S. Henning, F. Weichert and D. Suter
J. Magn. Reson. 235, 42--49 (2013)

[14] Optimized multiple-quantum filter for robust selective excitation of metabolite signals
M. Holbach, J. Lambert and D. Suter
J. Magn. Reson. 243, 8--16 (2014)

[15] Evidence for the light hole in GaAs/AlGaAs quantum wells from optically-pumped NMR and Hanle curve measurements
E. L. Sesti, W. A. Worthoff, D. D. Wheeler, D. Suter and S. E. Hayes
J. Magn. Reson. 246, 130--135 (2014)

[16] Tuner and radiation shield for planar electron paramagnetic resonance microresonators
R. Narkowicz and D. Suter
Review of Scientific Instruments 86, 024701 (2015)

[17] Optimized selective lactate excitation with a refocused multiple-quantum filter
M. Holbach, J. Lambert, S. Johst, M. E. Ladd and D. Suter
J. Magn. Reson. 255, 34--38 (2015)

[18] Stability and Permeability of Microcapsules for Controlled Drug Delivery from Magnetic Resonance Microscopy
chapter 9 of 'Microencapsulation and Microspheres for Food Applications'
D. Suter, P. Degen, D. Edelhoff and S. Henning
Editors: L. Sagis
Academic Press, 173-194 (2015)

[19] Anisotropic diffusion phantoms based on microcapillaries
S. Vellmer, D. Edelhoff, D. Suter and I. I. Maximov
Journal of Magnetic Resonance 279, 1 - 10 (2017)

[20] Validation of DWI pre-processing procedures for reliable differentiation between human brain gliomas
A. S. T. S. Vellmer and I. I. Maximov
Zeitschrift für Medizinische Physik 28, 14-24 (2018)

[21] NMR imaging of flow on the microscale
D. Suter and D. Edelhoff edited by Jens Anders and Jan G. Korvink
Micro and Nano Scale NMR,Wiley-VCH (2018)