Gadolinium-DOTA Contrast Agent Process With Dynamic pH Control
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Solution Overview
Problem
Existing methods for producing gadolinium-DOTA complexes as MR contrast agents face challenges in achieving equimolar stoichiometric ratios, leading to the presence of free gadolinium and requiring complex pH adjustments, making them industrially impractical and inefficient.
Innovation Solution
A method involving the use of equimolar amounts of gadolinium and DOTA, with pH regulation in the acidic range followed by adjustment to a less acidic pH with meglumine, ensuring complete complex formation without excess gadolinium, allowing for a simple and efficient industrial production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equimolar amounts of gadolinium and DOTA are used, then complete complex formation is achieved without free gadolinium, but the process requires precise pH regulation making it complex
Solution Approach 1:
Meglumine is used as an intermediary substance to regulate pH during the complex formation process. It serves as a buffering agent that maintains the pH in the critical range of 4.0-6.0, enabling complete complex formation without requiring complex multi-stage pH control systems. The meglumine acts as a mediator between the acidic DOTA and gadolinium salt, facilitating smooth complex formation.
Solution Approach 2:
The invention optimizes specific parameter ranges to simplify the process: maintaining pH between 4.0-6.0 (optimally 5.0-5.5), using molar ratios of DOTA to meglumine between 1:1.0-1:5.0 (optimally 1:1.2-1:1.5), and controlling the gadolinium salt to DOTA ratio at 1:0.95-1:1.05. These parameter specifications transform a potentially complex process into a controlled, reproducible industrial process.
2Ease of manufacture
If non-equimolar amounts of gadolinium and DOTA are used, then the process is simpler, but free gadolinium remains in the preparation
Solution Approach 1:
Meglumine is added preliminarily to the reaction mixture before or during the addition of gadolinium salt and DOTA. This preliminary action establishes the proper pH environment in advance, ensuring that when equimolar amounts of gadolinium and DOTA are mixed, complete complex formation occurs immediately without leaving free gadolinium. The meglumine is already in position to buffer any pH changes during complex formation.
Solution Approach 2:
The invention implements a feedback mechanism where the pH of the reaction mixture is monitored and adjusted by adding meglumine to maintain pH between 4.0-6.0. This feedback control ensures that the complex formation proceeds under optimal conditions, achieving complete reaction with equimolar reagents while keeping the process simple and industrially viable.
3Stability of the object's composition
If pH is adjusted to neutral range, then the preparation is more stable, but complex formation is incomplete
Solution Approach 1:
The invention uses a dynamic pH control strategy rather than fixing pH at a single neutral value. The pH is actively maintained in the acidic range of 4.0-6.0 during complex formation, then allowed to naturally increase to neutral range (6.5-7.5) after complex formation is complete. This dynamic approach ensures complete reaction during formation while achieving stability in the final product.
Solution Approach 2:
The meglumine continues to buffer the solution throughout the entire process, from complex formation through final product stabilization. This continuous buffering action maintains optimal pH during reaction, then supports the final stable neutral pH of the preparation, ensuring both complete complex formation and product stability without requiring separate processing steps.
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 method ensures the absence of free gadolinium, achieves high yields, and allows for reproducible production of gadolinium-DOTA complexes suitable for MR contrast agents with minimal by-products, suitable for industrial scale-up.
Implementation Method 1
adjusting the pH of the reaction mixture to a pH between 4.0 and 6.0 with a base, in particular with meglumine
Implementation Method 2
complex of a macrocyclic chelate, such as DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), with a lanthanide, such as gadolinium
Data Source
AI summary
A method produces an aqueous liquid preparation for magnetic resonance contrast that contains a complex of a lanthanide and a macrocyclic chelate together with free chelate. A solution of the macrocyclic chelate in water is prepared, lanthanide and meglumine are added, and complex formation proceeds in the presence of meglumine at a pH between 6.5 and 8.0 with lanthanide in molar excess over meglumine and meglumine in molar excess over the chelate. The pH is then reduced to a target value below 5.0 by incremental addition of an acid such as further chelate, optionally followed by addition of a fixed chelate amount. The pH is subsequently raised above 6.5 with meglumine and the solution is diluted to a final volume, providing an industrial-scale single-vessel process that yields a preparation containing a defined low amount of free lanthanide.