Periodic Reporting for period 1 - ZincMRI (Multifaceted molecular MRI toolbox to uncover Zn2+ in physiology and pathology)
Berichtszeitraum: 2023-04-01 bis 2025-09-30
Zinc ions (Zn²⁺) are essential for life. They are involved in nearly every major biological process- from immune function and brain activity to reproduction and cellular repair. Yet, unlike other ions, the behavior of zinc in living tissues remains poorly understood. Current imaging technologies, such as optical fluorescent imaging (using fluorescent dyes), can detect zinc in cells, but they are limited by light penetration, especially in deep tissues like the brain or internal organs. These techniques cannot be used reliably in larger animals or humans and often fail to provide full, quantitative information. Therefore, there is a growing need for non-invasive imaging tools that can reveal where zinc is, how it changes over time, and how it affects the expression of zinc-regulated genes throughout the body, in both health and disease.
ZincMRI responds to this need by developing a completely new kind of molecular imaging toolbox based on magnetic resonance imaging (MRI). The project combines two breakthrough approaches:
1. Activity-based 19F-MRI zinc sensors – these are synthetic molecules that produce a visible MRI signal when they react specifically with zinc ions, enabling real-time mapping of zinc dynamics with high specificity and no background interference.
2. Genetically encoded MRI reporter systems – these are engineered gene reporters that are activated only when cells detect excess zinc, triggering a secondary MRI-visible signal. This allows scientists to monitor gene expression controlled by zinc, a crucial part of how cells respond to stress, disease, or therapy.
By integrating both tools into a single, multifaceted platform, ZincMRI aims to deliver the first MRI-based system capable of simultaneously mapping zinc ion concentrations and zinc-dependent gene activity in living organisms. This dual approach offers a unique and powerful window into zinc biology, with spatial, temporal, and molecular resolution never achieved before. The impact of such a platform is potentially transformative. It can help researchers uncover how zinc contributes to the onset and progression of diseases, reveal new biomarkers for early diagnosis, and guide the development of zinc-targeted therapies.
ZincMRI responds to this need by developing a completely new kind of molecular imaging toolbox based on magnetic resonance imaging (MRI). The project combines two breakthrough approaches:
1. Activity-based 19F-MRI zinc sensors – these are synthetic molecules that produce a visible MRI signal when they react specifically with zinc ions, enabling real-time mapping of zinc dynamics with high specificity and no background interference.
2. Genetically encoded MRI reporter systems – these are engineered gene reporters that are activated only when cells detect excess zinc, triggering a secondary MRI-visible signal. This allows scientists to monitor gene expression controlled by zinc, a crucial part of how cells respond to stress, disease, or therapy.
By integrating both tools into a single, multifaceted platform, ZincMRI aims to deliver the first MRI-based system capable of simultaneously mapping zinc ion concentrations and zinc-dependent gene activity in living organisms. This dual approach offers a unique and powerful window into zinc biology, with spatial, temporal, and molecular resolution never achieved before. The impact of such a platform is potentially transformative. It can help researchers uncover how zinc contributes to the onset and progression of diseases, reveal new biomarkers for early diagnosis, and guide the development of zinc-targeted therapies.
Since the start of the ZincMRI project, significant scientific and technological progress has been made toward building a new molecular MRI platform for monitoring zinc ions (Zn²⁺) and zinc-regulated gene activity in living organisms.
1. Development of Zn²⁺-Responsive 19F-MRI Sensors (Activity-Based Sensing)
One major breakthrough was the design and validation of a synthetic, fluorinated molecular probe that reacts selectively with Zn²⁺. Upon interaction with zinc, the probe undergoes a chemical transformation that shifts its fluorine-19 (¹⁹F) NMR signal by 12 ppm, producing a sharp, background-free contrast in MRI scans. This "turn-on" contrast may enable, upon implementation in vivo, rapid, quantitative detection of transient zinc elevations in cells and tissues, including under conditions that mimic disease-related stress.
2. Implementation of Genetically Encoded MRI Reporters for Zinc-Regulated Gene Expression
To complement chemical sensing, a reporter system was engineered based on human thymidine kinase 1 (hTK1) and a deuterated nucleoside analog (d₃-thymidine). When cells express the hTK1 gene, they phosphorylate and retain the deuterated compound, which can then be detected with deuterium MRI (²H-MRI). This approach offers a fully orthogonal imaging channel, separate from both conventional proton (¹H) MRI, used for anatomical MRI, and ¹⁹F-MRI, used for Zn²⁺ sensing, enabling multiplexed detection of both zinc and gene expression in the same subject without signal interference. This system marks the first demonstration of in vivo gene expression imaging using a clinically relevant, non-mutated human enzyme and an unmodified, naturally derived imaging agent.
3. Integration and Validation of Orthogonal MRI Modalities
The two major components of ZincMRI, the synthetic and genetic components, are now being established and are ready to be integrated into a single, multifaceted MRI platform. Experiments confirmed the feasibility of simultaneous ¹⁹F-, ²H-, and ¹H-MRI imaging, showing the potential of dynamic zinc levels, gene expression, and anatomical context to be visualized together in phantoms and in vivo systems.
4. Extension Toward Ion Discrimination Technologies
A further achievement was the development of a magnetic resonance fingerprinting (MRF) strategy, based on ¹⁹F-paraGEST (paramagnetic guest exchange saturation transfer), that allows identification and quantification of different metal ions in complex mixtures. Although initially designed for lanthanides, this technology establishes the foundation for future extensions of ZincMRI to other biologically relevant metals.
1. Development of Zn²⁺-Responsive 19F-MRI Sensors (Activity-Based Sensing)
One major breakthrough was the design and validation of a synthetic, fluorinated molecular probe that reacts selectively with Zn²⁺. Upon interaction with zinc, the probe undergoes a chemical transformation that shifts its fluorine-19 (¹⁹F) NMR signal by 12 ppm, producing a sharp, background-free contrast in MRI scans. This "turn-on" contrast may enable, upon implementation in vivo, rapid, quantitative detection of transient zinc elevations in cells and tissues, including under conditions that mimic disease-related stress.
2. Implementation of Genetically Encoded MRI Reporters for Zinc-Regulated Gene Expression
To complement chemical sensing, a reporter system was engineered based on human thymidine kinase 1 (hTK1) and a deuterated nucleoside analog (d₃-thymidine). When cells express the hTK1 gene, they phosphorylate and retain the deuterated compound, which can then be detected with deuterium MRI (²H-MRI). This approach offers a fully orthogonal imaging channel, separate from both conventional proton (¹H) MRI, used for anatomical MRI, and ¹⁹F-MRI, used for Zn²⁺ sensing, enabling multiplexed detection of both zinc and gene expression in the same subject without signal interference. This system marks the first demonstration of in vivo gene expression imaging using a clinically relevant, non-mutated human enzyme and an unmodified, naturally derived imaging agent.
3. Integration and Validation of Orthogonal MRI Modalities
The two major components of ZincMRI, the synthetic and genetic components, are now being established and are ready to be integrated into a single, multifaceted MRI platform. Experiments confirmed the feasibility of simultaneous ¹⁹F-, ²H-, and ¹H-MRI imaging, showing the potential of dynamic zinc levels, gene expression, and anatomical context to be visualized together in phantoms and in vivo systems.
4. Extension Toward Ion Discrimination Technologies
A further achievement was the development of a magnetic resonance fingerprinting (MRF) strategy, based on ¹⁹F-paraGEST (paramagnetic guest exchange saturation transfer), that allows identification and quantification of different metal ions in complex mixtures. Although initially designed for lanthanides, this technology establishes the foundation for future extensions of ZincMRI to other biologically relevant metals.
The ZincMRI project has pushed the boundaries of what is currently possible in non-invasive molecular imaging. By integrating synthetic chemistry and genetic engineering into a unified MRI-based platform, the project introduces a first-of-its-kind system for mapping both labile Zn²⁺ ions and zinc-regulated gene expression in living organisms. This dual capability, using a single, non-radioactive imaging modality, is entirely new in the field.
Specific Breakthroughs in Molecular Imaging
• Activity-based ¹⁹F-MRI sensors: Most existing metal ion sensors rely on reversible binding mechanisms, which are often too slow or nonspecific to detect transient events. ZincMRI introduced an irreversible, Zn²⁺-triggered ¹⁹F-MRI probe that generates a strong, quantifiable, and background-free signal. This is a major step forward in sensitivity, speed, and specificity.
• ²H-MRI gene expression reporters: While genetically encoded optical reporters are widely used, their dependence on light limits their use in deep tissues and larger organisms. ZincMRI overcame this by creating the first in vivo ²H-MRI gene reporter system using a natural human enzyme (hTK1) and a non-toxic, clinically relevant nucleoside. This novel strategy enables truly non-invasive gene expression imaging with high biological compatibility and no background interference.
• Multinuclear, orthogonal MRI: The combination of ¹⁹F-, ²H-, and ¹H-MRI imaging within a single experiment, without signal cross-talk, is an unprecedented achievement in the field of biomedical imaging. This opens the door to real-time, multiplexed tracking of multiple biological processes simultaneously.
Overview of the Results
ZincMRI has delivered:
• A new class of fluorinated, activity-based MRI probes for metal ion imaging
• The first deuterium MRI reporter system based on a natural human gene
• A robust and validated framework for multiplexed, multinuclear MRI imaging
• A proof-of-concept for a translational platform that may change how we monitor metal ions and gene regulation in vivo
These outcomes have the potential to create new standards in biological sciences, medical diagnostics, and imaging science, supporting future developments in drug development, precision medicine, and targeted therapies.
Specific Breakthroughs in Molecular Imaging
• Activity-based ¹⁹F-MRI sensors: Most existing metal ion sensors rely on reversible binding mechanisms, which are often too slow or nonspecific to detect transient events. ZincMRI introduced an irreversible, Zn²⁺-triggered ¹⁹F-MRI probe that generates a strong, quantifiable, and background-free signal. This is a major step forward in sensitivity, speed, and specificity.
• ²H-MRI gene expression reporters: While genetically encoded optical reporters are widely used, their dependence on light limits their use in deep tissues and larger organisms. ZincMRI overcame this by creating the first in vivo ²H-MRI gene reporter system using a natural human enzyme (hTK1) and a non-toxic, clinically relevant nucleoside. This novel strategy enables truly non-invasive gene expression imaging with high biological compatibility and no background interference.
• Multinuclear, orthogonal MRI: The combination of ¹⁹F-, ²H-, and ¹H-MRI imaging within a single experiment, without signal cross-talk, is an unprecedented achievement in the field of biomedical imaging. This opens the door to real-time, multiplexed tracking of multiple biological processes simultaneously.
Overview of the Results
ZincMRI has delivered:
• A new class of fluorinated, activity-based MRI probes for metal ion imaging
• The first deuterium MRI reporter system based on a natural human gene
• A robust and validated framework for multiplexed, multinuclear MRI imaging
• A proof-of-concept for a translational platform that may change how we monitor metal ions and gene regulation in vivo
These outcomes have the potential to create new standards in biological sciences, medical diagnostics, and imaging science, supporting future developments in drug development, precision medicine, and targeted therapies.