Acidic pH Immunoassay for Protein A Quantification
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Solution Overview
Problem
Current methods for quantifying protein A in fluid samples, especially when it is in complex form with IgG, face challenges due to limited access to epitopes, leading to inaccurate concentration estimates and potential contamination issues during purification processes, which can result in unwanted side effects during therapeutic protein administration.
Innovation Solution
A method involving separate acidic pH steps for dissociating preformed protein A-IgG complexes, followed by an immunoassay at a pH that prevents reformation of complexes, allowing for accurate quantification of protein A using a ligand capable of specific binding, even in the presence of large amounts of complexing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protein A is quantified in complex form with IgG using conventional immunoassays, then the assay can be performed under physiological conditions, but the measurement precision deteriorates due to limited access to epitopes on complexed protein A
Solution Approach 1:
The patent applies parameter changes by shifting the pH from physiological conditions (pH 7.4) to acidic conditions (pH 2.0-3.0) to dissociate protein A-IgG complexes. This pH change disrupts the non-covalent interactions maintaining the complex, freeing epitopes on protein A for antibody binding and enabling accurate quantification of total protein A including previously complexed forms.
2Productivity
If affinity purification is performed using protein A immobilized on resin, then the purification efficiency is improved, but the harmful factors increase due to ligand leaching and contamination of the purified product
Solution Approach 1:
The patent replaces the conventional affinity purification method with acid-based dissociation. Instead of relying on protein A-IgG binding at physiological pH, the method uses acidic conditions (pH 2.0-3.0) to dissociate complexes and release IgG from the protein A resin, preventing ligand leaching contamination while maintaining purification efficiency.
Solution Approach 2:
The patent changes the pH parameter from physiological conditions to acidic conditions during the purification process. This parameter change prevents ligand leaching by disrupting the binding interaction between protein A and IgG, thereby eliminating contamination of the purified therapeutic protein with leached ligand.
3Ease of operation
If conventional immunoassays are used to detect protein A, then the ease of operation is maintained, but the measurement precision deteriorates when protein A is present in complex form with antibodies
Solution Approach 1:
The patent modifies the assay conditions by changing the pH parameter to acidic conditions (pH 2.0-3.0). This single parameter change achieves both complex dissociation and maintains assay functionality, preserving ease of operation while dramatically improving measurement precision for total protein A quantification.
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 precise determination of protein A concentrations at sub-ppm levels, reducing the risk of unwanted side effects by ensuring accurate quantification and minimizing complex reformation, thus improving the safety and efficacy of therapeutic protein purification.
Implementation Method 1
subjecting the sample to a first acidic pH in the range from about 1.5 to about 3.2 to at least substantially dissociate any analyte complex present
Implementation Method 2
subjecting the sample to a first acidic pH in the range from about 1.5 to about 3.2 to at least substantially dissociate any analyte complex present and provide substantially all analyte in free form
Implementation Method 3
determining the binding of analyte to the ligand to quantitatively determine the analyte in the sample, wherein the ligand is capable of specifically binding to the analyte
Data Source
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AI summary
A method of quantitatively determining an analyte in a fluid sample by an immunoassay comprises binding of the analyte to a ligand capable of specifically binding to the analyte, wherein at least part of the analyte is present as an analyte complex is disclosed. The method comprises the steps of: a) subjecting the sample to a first acidic pH to at least substantially dissociate any analyte complex present and provide substantially all analyte in free form, b) raising the first acidic pH to a second acidic pH where re-formation of complexes is prevented but where binding of analyte to the ligand is permitted, and c) determining the binding of analyte to the ligand to quantitatively determine the analyte in the sample.