Ligand-Guided Selection for Aptamer Specificity
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Solution Overview
Problem
Current methods for selecting aptamers, such as cell-SELEX, face challenges in identifying aptamers that specifically recognize predetermined antigens in their endogenous state without prior or post-manipulation of receptor proteins, limiting their clinical practicality and therapeutic applications.
Innovation Solution
The Ligand-guided-Selection (LIGS) method introduces a stronger, specific ligand (e.g., an antibody) to displace aptamers from a partially enriched SELEX pool, allowing for the elution and amplification of aptamers specific to a predetermined antigen, thereby enhancing specificity and efficiency in identifying aptamers that bind to antigens in their native state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional SELEX method is used to screen aptamers against target cells, then a large number of aptamers can be generated, but the aptamers cannot specifically recognize predetermined antigens in their endogenous state without prior manipulation
Solution Approach 1:
The patent segments the SELEX process into two distinct phases: (1) initial enrichment against whole cells to generate a diverse aptamer pool, and (2) subsequent antigen-specific selection using purified antigens to identify aptamers specific to predetermined antigens. This segmentation allows the method to first generate quantity (phase 1) and then achieve specificity (phase 2), resolving the contradiction between generating many aptamers and achieving antigen-specific recognition.
Solution Approach 2:
The patent extracts the predetermined antigen from the complex cellular environment and uses it as a separate selection target. By taking out the antigen in its purified form and using it to screen the enriched aptamer pool, the method enables identification of aptamers that specifically recognize the antigen in its endogenous state without requiring prior manipulation of receptor proteins on whole cells.
2Reliability
If aptamers are selected against whole cells, then aptamers can bind to cell surfaces, but it is difficult to determine which specific antigen is recognized
Solution Approach 1:
The patent introduces purified predetermined antigens as an intermediary substance that mediates between the aptamer pool and the specific antigen target. By using the antigen as an intermediary selection target, the method maintains the reliability of cell surface binding (since the antigen is derived from the cell) while simultaneously enabling easy identification of the specific antigen recognized, as the antigen itself serves as the selection criterion.
Solution Approach 2:
Instead of trying to identify which antigen an aptamer binds to by analyzing binding patterns on whole cells (difficult direction), the patent inverts the approach by using known purified antigens to select aptamers (easy direction). This inversion makes the identification process straightforward: aptamers that bind to the purified antigen during selection are guaranteed to recognize that specific antigen, eliminating the detection difficulty.
3Strength
If SELEX is performed with multiple rounds of enrichment, then high-affinity binders are obtained, but the process requires prior manipulation of receptor proteins
Solution Approach 1:
The patent performs preliminary enrichment against whole cells before the antigen-specific selection step. This preliminary action generates a pre-enriched pool of aptamers with high binding affinity for cell surfaces, which then serves as the input for the second phase using purified antigens. By doing the enrichment work first (preliminary action), the subsequent antigen-specific selection becomes simpler and does not require complex manipulation of receptor proteins during the actual antigen-binding assays.
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
LIGS enables the identification of highly specific aptamers that target specific antigens with higher affinity and specificity, overcoming the limitations of traditional methods by selectively separating aptamers based on their interaction with antigens in their native conformation, which can be applied to various platforms including phage-display libraries and small-molecule libraries.
Implementation Method 1
treating the ligand-cell complex with a predetermined ligand that is specific to the antigen, the predetermined ligand displacing ligands that are bound to the antigen
Data Source
AI summary
A Ligand-guided-Selection (LIGS) method for identifying highly specific aptamers against a predetermined antigen of a target is provided. LIGS uses a stronger and highly specific bivalent binder (e.g. an antibody) interacting with its cognate antigen to displace specific aptamers from an enriched SELEX pool. Elution of the displaced aptamers provides aptamers that are specific to the predetermined antigen.