Mass Spectrometry Quantitation of Chromogranin A Without Immunoassays
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Solution Overview
Problem
Current immunoassays for measuring chromogranin A (CgA) in blood face challenges due to non-specific binding and reduced dynamic range, limiting their effectiveness in diagnostic laboratories.
Innovation Solution
A method for detecting CgA using mass spectrometry, involving purification, ionization, and quantitation of CgA ions through techniques like solid phase extraction, enzymatic digestion, and liquid chromatography, without the use of antibodies, enabling precise measurement of CgA levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If immunoassays are used to measure chromogranin A, then the measurement can be performed with standard laboratory equipment, but non-specific binding and reduced dynamic range occur
Solution Approach 1:
The patent replaces the immunoassay system (which relies on antibody-antigen binding) with a mass spectrometry-based system that uses peptide sequencing and mass-to-charge ratio detection. This substitution eliminates non-specific binding issues inherent in antibody-based assays while maintaining laboratory implementability through standardized MS protocols.
Solution Approach 2:
The patent changes the detection parameter from signal intensity (as in immunoassays) to mass-to-charge ratio and peptide sequence identification. This parameter transformation enables precise quantification without the dynamic range limitations of antibody-based methods, as mass spectrometry can accurately detect and quantify peptides across a wide concentration range.
2Ease of manufacture
If immunoassays are used for chromogranin A measurement, then the assay can be performed with standard equipment, but dynamic range is reduced requiring sample dilution
Solution Approach 1:
The patent substitutes the immunoassay detection mechanism with mass spectrometry, which inherently provides a wider dynamic range. The MS system can detect and quantify chromogranin A peptides across multiple orders of magnitude without requiring sample dilution, as the mass-to-charge ratio detection is linear and not saturation-limited like antibody binding assays.
3Measurement precision
If mass spectrometry is used to detect chromogranin A, then measurement precision and sensitivity are improved, but the complexity of the detection system increases
Solution Approach 1:
The patent segments the chromogranin A protein into specific peptide fragments through enzymatic digestion (e.g., using trypsin). This segmentation allows the mass spectrometry system to detect and quantify specific peptide sequences (such as residues 1-10 or 11-20) rather than requiring analysis of the entire protein, thereby reducing the complexity of the measurement process while maintaining high precision.
Solution Approach 2:
The patent introduces an intermediary step of enzymatic digestion to convert the complex chromogranin A protein into simpler peptide fragments that are more suitable for mass spectrometry analysis. This intermediary process simplifies the detection requirement, allowing standard MS instruments to achieve precise quantification without requiring complex sample preparation or specialized instrumentation.
4Measurement precision
If chromogranin A is purified and ionized for mass spectrometry, then detection sensitivity is enhanced, but the sample preparation steps increase
Solution Approach 1:
The patent performs preliminary enzymatic digestion of chromogranin A into peptides before mass spectrometry analysis. This preliminary action simplifies subsequent purification steps and enhances detection sensitivity, as the peptide fragments are more volatile and ionizable than the intact protein, requiring less extensive sample preparation while achieving higher MS detection sensitivity.
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 provides accurate and sensitive quantitation of CgA with a low limit of detection and quantitation, suitable for diagnosing neuroendocrine tumors and monitoring treatment response, with high reproducibility and wide linear range.
Implementation Method 1
purifying CgA in the sample comprising subjecting the sample to solid phase extraction
Implementation Method 2
enzymatically digesting the CgA
Implementation Method 3
subjecting the CgA to liquid chromatography
Implementation Method 4
the ionization comprises electrospray ionization (ESI)
Implementation Method 5
the ionization comprises atmospheric pressure chemical ionization (APCI)
Implementation Method 6
determining the amount of the ion(s) from step (b) by mass spectrometry, measuring the amount of fragment ion having a mass-to-charge ratio of 831.5 ± 0.5 or 989.5 ± 0.5
Data Source
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AI summary
Provided are methods for detecting chromogranin A by mass spectrometry. In another aspect, provided herein are methods for quantitating chromogranin A by mass spectrometry. In another aspect, provided herein are methods for prognosis of or measuring the size of neuroendocrine tumors by mass spectrometry.