Metal Complex Radiolabelling via Hydrogen Bonding
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Solution Overview
Problem
Current methods for 18F radiolabelling of biological molecules, such as peptides, face challenges due to hydrogen bonding interactions with fluoride and require higher temperatures or narrow pH ranges, which can lead to degradation or instability, limiting the efficiency and compatibility with various biomolecules.
Innovation Solution
A method involving a metal complex with a trivalent metal ion and a tridentate triamine chelating agent, where hydrogen bonding is incorporated to facilitate fluoride incorporation at room temperature and in aqueous conditions, allowing for high affinity and stability of the 18F-labelled agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If standard nucleophilic substitution methods are used for 18F radiolabelling, then fluoride incorporation can be achieved, but hydrogen bonding interactions with amino acid functionalities reduce nucleophilicity and require higher temperatures
Solution Approach 1:
A metal complex (aluminium, gallium, indium, or thallium) is introduced as an intermediary to coordinate with the fluoride ion, forming a metal-fluoride complex that serves as the active radiolabelling species. This intermediary approach allows fluoride incorporation at lower temperatures while maintaining high efficiency, as the metal complex mediates the interaction between fluoride and the biological molecule.
Solution Approach 2:
The invention changes the chemical state of fluoride from free ion to metal-coordinated complex, fundamentally altering its reactivity parameters. This parameter change enables the radiolabelling reaction to proceed at lower temperatures (room temperature or physiological temperature) while maintaining high productivity, resolving the contradiction between reaction efficiency and temperature requirements.
2Productivity
If higher temperatures are used to overcome hydrogen bonding interactions, then fluoride incorporation efficiency improves, but peptide/protein structure degradation or disruption occurs
Solution Approach 1:
The metal complex acts as a protective intermediary that enables fluoride incorporation under mild conditions. By coordinating fluoride and facilitating its transfer to the biological molecule at lower temperatures, the metal complex prevents thermal degradation of peptide and protein structures while maintaining high incorporation efficiency.
Solution Approach 2:
Changing fluoride from free ion to metal-coordinated complex alters the reaction parameters, allowing the process to occur at temperatures that preserve biomolecule structural stability. This parameter change resolves the contradiction between achieving high fluoride incorporation and maintaining peptide/protein integrity.
3Reliability
If aluminium is used as the metal for fluoride binding, then strong metal-fluoride bond and in vivo stability are achieved, but the pH range for radiolabelling is narrow and requires acid conditions
Solution Approach 1:
The invention presents a universal platform using four different metals (aluminium, gallium, indium, thallium) that all provide strong fluoride binding and in vivo stability. This multi-metal approach offers versatility, allowing selection of the appropriate metal based on the specific biological molecule's pH sensitivity and other requirements, thus resolving the contradiction between stability and adaptability.
4Manufacturing precision
If the radiosynthesis process is extended to optimize labelling conditions, then radiolabelling quality improves, but yield loss due to radioactive decay increases
Solution Approach 1:
The metal complex intermediary enables rapid radiolabelling reactions that proceed to high quality completion in minimal time. The metal-fluoride complex reacts efficiently with biological molecules, achieving optimal radiolabelling quality while minimizing synthesis time and thus reducing radioactive decay losses.
Solution Approach 2:
The parameter change from free fluoride to metal-coordinated fluoride fundamentally accelerates the radiolabelling kinetics, allowing high-quality labelling to be achieved rapidly. This kinetic enhancement resolves the contradiction between achieving optimal radiolabelling quality and minimizing time loss to radioactive decay.
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
This approach enables efficient 18F radiolabelling of biomolecules under mild conditions, ensuring high in vivo stability and reducing the complexity and time of the radiosynthesis process, thereby minimizing yield loss due to radioactive decay.
Implementation Method 1
The invention highlights the incorporation of hydrogen bonding (H-bonding) into the metal complex scaffold, and how this can be utilised to improve the kinetics of fluoride incorporation
Implementation Method 2
A method involving a metal complex with a trivalent metal ion and a tridentate triamine chelating agent, where hydrogen bonding is incorporated to facilitate fluoride incorporation
Implementation Method 3
the aluminium-fluoride bond is one of the strongest metal-fluoride bonds, and the AlFn complex is stable in vivo
Data Source
AI summary
A method of labelling biological molecules with 18F, via attachment of fluorine to a metal complex, where the metal complex is conjugated to the biological molecule. The invention highlights the incorporation of hydrogen bonding (H-bonding) into the metal complex scaffold, and how this can be utilised to improve the kinetics of fluoride incorporation. Also provided are pharmaceutical compositions, kits and methods of in vivo imaging.