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Updated: Jan 19, 2026
Magnetic and Thermal-sensitive PolyN-isopropylacrylamide-based Microgels for Magnetically Triggered Controlled Release
Published on: July 4, 2017
Multi-contrast magnetic particle imaging for tomographic pH monitoring using stimuli-responsive hydrogels
Bruno Kluwe1,2, Justin Ackers3, Matthias Graeser3,4
1Fraunhofer IMTE, Fraunhofer Research Institution for Individualized and Cell-Based Medical Engineering, Lübeck, Germany. bruno.kluwe@ptb.de.
Abstract:
Magnetic particle imaging (MPI) is a tomographic imaging technique which determines the spatial distribution of magnetic nanoparticles (MNPs). Multi-contrast MPI provides the ability to detect environmental conditions of MNPs, such as temperature or viscosity. One parameter that has not been investigated but shows high potential for medical diagnosis is the pH value, as it is an indicator of inflamed or tumorous tissue. In this work, we present an approach to resolve the pH value using multi-contrast MPI. Our proof-of-concept is based on a stimuli-responsive, magnetic hydrogel that exhibits reversible swelling in response to a pH change. The pH contrast is generated indirectly via the pH-responsive hydrogel swelling modulating the signal of embedded MNPs. Magnetic particle spectrometry measurements show that the hydrogels' magnetic response correlates with the pH value, which could provide a new way of contactless pH monitoring. Finally, the feasibility of resolving different pH values in a multi-contrast MPI image is demonstrated.
Insights
This study introduces a novel method using multi-contrast magnetic particle imaging (MPI) to detect pH levels. A pH-responsive hydrogel modulates magnetic nanoparticle signals, enabling contactless pH monitoring for potential medical diagnostics.
Area of Science:
- Biomedical Imaging
- Materials Science
- Nanotechnology
Background:
- Magnetic particle imaging (MPI) is a tomographic technique for visualizing magnetic nanoparticle (MNP) distribution.
- Multi-contrast MPI can assess MNP environments like temperature and viscosity.
- pH is a crucial biomarker for conditions such as inflammation and tumors, but lacks non-invasive imaging methods.
Purpose of the Study:
- To develop and demonstrate a method for resolving pH values using multi-contrast MPI.
- To explore the potential of pH monitoring for medical diagnosis via MPI.
Main Methods:
- Utilized a stimuli-responsive magnetic hydrogel that swells reversibly with pH changes.
- Generated pH contrast indirectly by hydrogel swelling modulating the MNP signal.
- Employed magnetic particle spectrometry to correlate hydrogel magnetic response with pH.
- Demonstrated feasibility in a multi-contrast MPI imaging setting.
Main Results:
- Magnetic particle spectrometry confirmed that hydrogel magnetic response correlates with pH.
- The pH-responsive hydrogel effectively modulated MNP signals based on environmental pH.
- Successful demonstration of resolving different pH values within a multi-contrast MPI image.
Conclusions:
- Developed a proof-of-concept for contactless pH monitoring using multi-contrast MPI.
- Magnetic hydrogels offer a novel approach for pH-dependent signal modulation in MPI.
- This technique shows potential for future medical diagnostic applications by imaging pH variations.
