Iron Core SAXS Characterization in Iron Sucrose Colloids
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Solution Overview
Problem
Current methods for characterizing the size of iron cores in iron carbohydrate colloid complexes, such as iron sucrose, are unreliable due to the colloidal structure and nanometer size range, leading to inaccurate measurements and variability in results across different techniques like light scattering, atomic force microscopy, and cryogenic transmission electron microscopy.
Innovation Solution
The use of small-angle X-ray scattering (SAXS) to characterize the average particle diameter and size distribution of iron core nanoparticles by configuring an X-ray diffractometer in parallel beam transmission geometry and performing SAXS on samples with and without iron, allowing for background subtraction and modeling to determine the iron core size without sample manipulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light scattering method is used to characterize iron core size, then particle size characterization can be performed, but the colloidal structure and multiple sucrose particles surrounding the iron core render the method ineffective for characterizing the iron core size specifically
Solution Approach 1:
The patent segments the iron sucrose complex into two distinct components: the iron core and the surrounding sucrose shell. By using small-angle X-ray scattering with contrast variation techniques, the method selectively probes the iron core while treating the sucrose shell as a separate, removable background signal. This segmentation allows independent characterization of the iron core size despite the complex colloidal structure.
Solution Approach 2:
The patent extracts the iron core signal from the total scattering signal by performing background subtraction. The scattering pattern of pure sucrose (without iron) is measured and subtracted from the scattering pattern of iron sucrose, isolating the contribution from the iron core. This extraction technique enables accurate iron core size measurement without interference from the surrounding sucrose particles.
2Measurement precision
If atomic force microscopy is used to characterize iron core size, then particle size measurement can be attempted, but the method cannot produce stable results due to large fluctuations
Solution Approach 1:
The patent replaces the mechanical contact-based atomic force microscopy method with a non-contact X-ray scattering technique. Small-angle X-ray scattering uses electromagnetic radiation instead of mechanical probes to interrogate the iron core structure, eliminating the large fluctuations and instability inherent in AFM measurements of colloidal systems. This substitution provides more reliable and reproducible results.
3Measurement precision
If sample manipulation is performed to characterize iron core size, then certain measurements can be obtained, but the iron core may be perturbed from its native state leading to inaccurate results
Solution Approach 1:
The patent employs a methodology where the iron sucrose complex characterizes itself in its native state. The X-ray scattering experiment is performed on the intact iron sucrose complex without any manipulation, and the iron core size is extracted through computational analysis of the scattering data. The contrast variation and background subtraction techniques allow the system to reveal its own structural parameters without external perturbation.
4Measurement precision
If conventional particle size characterization methods are used, then overall particle size can be measured, but the nanometer size range and colloidal structure make it difficult to accurately characterize the iron core size specifically
Solution Approach 1:
The patent transitions from direct real-space imaging methods to reciprocal space analysis using X-ray scattering. By measuring scattering intensity as a function of scattering angle (momentum transfer), the method accesses structural information in reciprocal space that can be transformed to reveal real-space dimensions. This dimensional transformation enables precise measurement of nanometer-scale iron core sizes that are difficult to resolve with conventional direct imaging methods.
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 method provides accurate and reliable characterization of iron core size in iron carbohydrate colloid products, overcoming the limitations of existing techniques by maintaining the iron core in its unperturbed state and not requiring apriori knowledge of the substructure, with results matching those from other methods like AFM and cryo-TEM.
Implementation Method 1
small-angle X-ray scattering (SAXS) methods for characterizing the iron core of iron carbohydrate colloid drug products
Data Source
AI summary
The present disclosure introduces methods for characterizing iron core carbohydrate colloid drug products, such as iron sucrose drug products. Disclosed methods enable the characterization of the iron core size of the iron core nanoparticles in iron carbohydrates as they exist in the formulation in solution, such as e.g. iron sucrose drug products, and more particularly, the average particle diameter size and size distribution(s) of the iron core nanoparticles. The disclosed methods apply small-angle X-ray scattering (SAXS) in parallel beam transmission geometry, with a sample mounted inside a capillary and centered in the X-ray beam, to iron carbohydrates, such as iron sucrose, in solution without the need to modify the sample, such as to remove unbound carbohydrates, dilute, or dry the sample, to accurately characterize the average iron core particle diameter size of the iron core nanoparticles. An example application of the disclosed method is to perform SAXS measurements under identical instrument settings on two samples of the same type of iron core nanoparticle colloid drug product for the purpose of comparing their iron core structures. Such comparisons are typically performed during the iron core carbohydrate colloid drug development process, and can include comparisons of samples that have been manipulated.