Macrocyclic Fe(II) paraCEST MRI Contrast Agents
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Solution Overview
Problem
Current Magnetic Resonance Imaging (MRI) contrast agents face challenges in achieving high sensitivity and specificity, particularly in pH and temperature sensing, due to limitations in proton resonance shifting and stability, especially with endogenous macromolecule interactions and biological relevance.
Innovation Solution
Development of macrocyclic compounds complexed with Fe(II) or Ni(II) transition metal ions, featuring pendant donors and exchangeable protons, which act as paraCEST MRI contrast agents, providing pH and temperature-dependent sensing capabilities through highly shifted proton resonances and kinetic inertness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI contrast agents are used, then imaging can be performed, but sensitivity and specificity are limited due to insufficient proton resonance shifting
Solution Approach 1:
The patent changes the chemical and physical parameters of the contrast agent by using macrocyclic compounds with Fe(II) or Ni(II) metal ions coordinated to pendant donors. This coordination geometry and metal ion selection produces highly shifted proton resonances, fundamentally altering the magnetic properties to achieve both high sensitivity and reliability in pH and temperature sensing
Solution Approach 2:
The invention creates a composite structure where Fe(II) or Ni(II) metal ions are coordinated within macrocyclic ligands containing pendant donors. This composite molecular architecture combines the magnetic properties of transition metal ions with the structural stability and chemical tunability of macrocyclic frameworks, enabling enhanced proton resonance shifting while maintaining kinetic inertness
2Measurement precision
If contrast agents with higher sensitivity are developed, then imaging precision improves, but stability and kinetic inertness may be compromised
Solution Approach 1:
The patent applies local quality by creating distinct functional regions within the macrocyclic compound: the metal ion coordination site provides kinetic inertness and stability, while the pendant donors and exchangeable protons provide pH and temperature sensitivity. This spatial separation of functions allows both high sensing precision and compositional stability to coexist
Solution Approach 2:
The invention uses Fe(II) or Ni(II) metal ions which are biologically relevant and naturally present in the body, replacing less stable or more toxic metals. These metal ions provide both the necessary magnetic properties for high-precision sensing and inherent biocompatibility, effectively using 'natural' materials that are both sensitive and stable in physiological environments
3Measurement precision
If contrast agents are designed for enhanced pH and temperature sensing, then imaging specificity improves, but endogenous macromolecule interactions increase causing instability
Solution Approach 1:
The patent extracts the sensing function from interactions with endogenous macromolecules by designing a self-contained sensing mechanism within the macrocyclic compound itself. The pH and temperature sensitivity arises from the coordination chemistry of the metal ion with pendant donors and exchangeable protons, not from interactions with external biomolecules, thereby eliminating harmful interactions while maintaining sensing specificity
Solution Approach 2:
The macrocyclic ligand acts as an intermediary between the metal ion and the physiological environment. It provides a stable coordination sphere that prevents direct interaction between the metal ion and endogenous macromolecules, while still allowing the complex to sense pH and temperature changes through its internal chemistry, thus mediating between stability requirements and sensing functionality
4Measurement precision
If macrocyclic compounds with pendant donors are used, then proton resonance shifting increases, but molecular complexity increases
Solution Approach 1:
The patent segments the macrocyclic compound into distinct functional modules: the macrocyclic core provides structural stability and kinetic inertness, pendant donors provide coordination sites for enhanced proton resonance shifting, and exchangeable protons provide pH and temperature sensitivity. This modular segmentation allows each component to contribute specifically to the overall performance without requiring complete redesign of the entire molecule
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The macrocyclic compounds enhance MRI contrast by offering stable, pH and temperature-sensitive imaging, avoiding endogenous macromolecule interactions and ensuring safety by leveraging biological relevance of iron, thus improving imaging sensitivity and specificity.
Implementation Method 1
These complexes may have properties that change with pH and temperature and so can be used as pH and temperature dependent sensors. Fe(II) and Ni(II) have short electronic relaxation times and favorable paramagnetic properties for producing large proton shifts.
Implementation Method 2
Fe(II) and Ni(II) have short electronic relaxation times (10-11 to 10-12 s-1) and favorable paramagnetic properties for producing large proton shifts.
Data Source
AI summary
Provided are macrocyclic compounds having a macrocyclic core which has at least one macrocyclic donor and at least one pendant group which has at least one donor group. The macrocyclic compounds can be complexed to Fe(II) and Ni(II). The macrocyclic compounds can be used in imaging methods. For example, the compounds can be used MRI paraCEST contrast agents.