Related Experiment Video
Updated: Jul 7, 2026
DNA-magnetic Particle Binding Analysis by Dynamic and Electrophoretic Light Scattering
Published on: November 9, 2017
Magnetic microparticle aggregation for viscosity determination by MR
Rui Hong1, Michael J Cima, Ralph Weissleder
1Center for Molecular Imaging Research, Harvard Medical School, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
Abstract:
Micron-sized magnetic particles were induced to aggregate when placed in homogeneous magnetic fields, like those of MR imagers and relaxometers, and then spontaneously returned to their dispersed state when removed from the field. Associated with the aggregation and dispersion of the magnetic particles were time-dependent increases and decreases in the spin-spin relaxation time (T2) of the water. Magnetic nanoparticles, with far smaller magnetic moments per particle, did not undergo magnetically induced aggregation and exhibited time-independent values of T2. The rate of T2 change associated with magnetic microparticle aggregation was used to determine the viscosity of liquid samples, providing a method that can be of particular advantage for determining the viscosity of small volumes of potentially biohazardous samples of blood or blood plasma.
Insights
Micron-sized magnetic particles aggregate in magnetic fields, altering water relaxation times (T2). This T2 change allows for viscosity measurements, especially useful for small, biohazardous samples.
Area of Science:
- Biophysics
- Materials Science
- Analytical Chemistry
Background:
- Magnetic particles respond to external magnetic fields.
- Water's spin-spin relaxation time (T2) is sensitive to its environment.
- Viscosity measurement is crucial in various scientific fields.
Purpose of the Study:
- To investigate the relationship between magnetic microparticle aggregation and water T2 relaxation.
- To develop a novel method for determining liquid viscosity using magnetic particle behavior.
- To assess the utility of this method for analyzing small or biohazardous liquid samples.
Main Methods:
- Inducing aggregation of micron-sized magnetic particles in homogeneous magnetic fields.
- Measuring time-dependent changes in water spin-spin relaxation time (T2) during aggregation and dispersion.
- Comparing the behavior of micron-sized particles with magnetic nanoparticles.
- Correlating the rate of T2 change with sample viscosity.
Main Results:
- Micron-sized magnetic particles aggregated in magnetic fields, causing time-dependent changes in water T2.
- Magnetic nanoparticles did not aggregate and showed time-independent T2 values.
- The rate of T2 change was successfully used to determine liquid sample viscosity.
- The method demonstrated particular advantage for small volumes of blood or plasma.
Conclusions:
- Magnetically induced aggregation of microparticles influences water T2 relaxation.
- This phenomenon provides a basis for a new viscosity measurement technique.
- The developed method is advantageous for analyzing small, potentially biohazardous liquid samples like blood plasma.
