Click Chemistry Signal Amplification for Low-Background IHC and ISH
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Solution Overview
Problem
Existing signal amplification methods in immunohistochemistry (IHC) and in situ hybridization (ISH) assays, such as Tyramide Signal Amplification (TSA) and Quinone Methide Signal Amplification (QMSA), suffer from non-specific background signal amplification, solubility issues with fluorophores and chromophores, and limited ability to amplify beyond a certain saturation point, affecting the detection of low-abundance cellular markers.
Innovation Solution
The use of click chemistry to covalently bind reporter molecules to tissue through click conjugates, which include specific functional groups and linkers, allowing for improved signal amplification without increasing background noise and overcoming solubility challenges, enabling the use of a wider range of reporters and additional color spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal amplification is performed using TSA or QMSA methods, then detection sensitivity is improved, but non-specific background signal increases
Solution Approach 1:
The patent segments the amplification process into two distinct stages: first, enzyme-catalyzed deposition of reactive intermediates at target sites; second, click chemistry coupling of reporter molecules to these deposited intermediates. This segmentation allows the amplification function to be separated from the detection function, enabling high sensitivity while reducing background signal from non-specific reporter deposition.
Solution Approach 2:
The patent introduces click chemistry conjugates as intermediaries between the enzyme-catalyzed amplification step and the final detection step. These conjugates contain reactive groups that specifically couple to the deposited intermediates, acting as a bridge that transfers the amplified signal while maintaining spatial specificity and reducing non-specific background.
2Illumination intensity
If conventional amplification methods are used, then signal intensity is increased, but solubility issues with fluorophores and chromophores arise
Solution Approach 1:
The patent changes the chemical parameters of the reporter molecules by using click chemistry conjugates with modified solubility properties. The conjugates incorporate solubilizing groups and linkers that maintain the fluorescent or chromogenic properties while improving solubility in aqueous buffers, allowing high signal intensity without precipitation or aggregation.
3Measurement precision
If amplification is performed to detect low-abundance markers, then diagnostic accuracy is improved, but background noise obscures faint signals
Solution Approach 1:
By separating the amplification step (enzyme-catalyzed deposition) from the detection step (click chemistry coupling), the patent enables specific amplification at target sites without proportional amplification of background noise. The click chemistry reaction occurs only where the reactive intermediates have been deposited, preserving signal-to-noise ratio even for low-abundance markers.
Solution Approach 2:
The patent implements a feedback mechanism where the enzyme-catalyzed deposition creates a localized reservoir of reactive intermediates that then guides the subsequent click chemistry coupling. This feedback loop ensures that reporter molecules are deposited only at sites where the target antigen or nucleic acid is present, enhancing detection of low-abundance markers while minimizing background noise.
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
Enhances staining intensity and quality, allows visualization of low-abundance markers, and expands the color palette in IHC and ISH assays by stabilizing reporters and optimizing solubility, thus improving diagnostic accuracy.
Implementation Method 1
The use of click chemistry to covalently bind reporter molecules to tissue through click conjugates
Implementation Method 2
catalyzed reporter deposition to amplify the detectable label signal. Catalysis of an enzyme in a CARD or TSA method is enhanced by reacting a labeled phenol molecule with an enzyme
Implementation Method 3
TSA takes advantage of the reaction between horseradish peroxidase (HRP) and tyramide. In the presence of H2O2, tyramide is converted to a highly-reactive and short-lived radical intermediate that reacts preferentially with electron-rich amino acid residues on proteins
Data Source
AI summary
Applicants have developed an amplification system and methodology for IHC and ISH staining that utilizes “click chemistry” to covalently bind reporter molecules to tissue.