X-Aptamers for SNAP25 Detection via Modified Nucleotides
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Solution Overview
Problem
Aptamers face challenges in stability and versatility, particularly when targeting acidic proteins, due to their high sensitivity to nuclease digestion and limited affinity, which hinders their use in vivo and batch-to-batch consistency, making them impractical for therapeutic applications compared to antibodies.
Innovation Solution
Development of X-aptamers with modified nucleotides such as indols, amines, and phenols, which are more stable and versatile, allowing for specific binding to human SNAP25 and its fragments through a bead-based split synthesis selection process, enhancing nuclease resistance and binding affinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional aptamers are used for detecting SNAP25, then they provide high binding affinity through three-dimensional structure, but they exhibit high sensitivity to nuclease digestion making them unstable for in vivo administration
Solution Approach 1:
The patent applies composite materials by combining modified nucleotides (5-X-dU, 5-X-dT, 6-X-dA) with standard nucleotides to create chimeric aptamers. These composite structures incorporate chemically modified bases that resist nuclease digestion while maintaining the three-dimensional folded structure necessary for SNAP25 binding. The modified nucleotides provide both structural integrity and enzymatic resistance, resolving the contradiction between stability and binding affinity.
Solution Approach 2:
The patent changes the chemical parameters of the nucleotide building blocks by introducing various substituents at the 5-position of uracil/thymine and 6-position of adenine. These parameter changes in the chemical structure of nucleotides fundamentally alter the aptamer's resistance to nuclease digestion while preserving or enhancing its ability to form stable three-dimensional binding structures for SNAP25 detection.
2Ease of manufacture
If aptamers are used as alternatives to antibodies, then they are approximately 100-fold less expensive to produce, but they have limited affinity towards acidic proteins due to lack of cationic groups
Solution Approach 1:
The patent changes the electrochemical parameters of the aptamer by incorporating cationic modified nucleotides (such as 6-X-dA with basic side chains). This parameter change introduces positive charges that can interact with acidic (negatively charged) regions of target proteins like SNAP25, thereby expanding the aptamer's versatility to bind acidic proteins while maintaining the cost-effective manufacturing advantage.
Solution Approach 2:
The patent creates composite nucleotide structures that combine the polyanionic backbone of DNA/RNA with cationic side chain modifications. This composite approach allows the aptamer to maintain its inherent structural stability and low production cost while gaining the ability to interact electrostatically with acidic protein surfaces, thus improving adaptability.
3Stability of the object's composition
If post-selection modification is applied to enhance oligonucleotide stability, then in vivo stability is improved, but the three-dimensional structure of the aptamer is affected which compromises its ability to bind to the target
Solution Approach 1:
The patent applies preliminary action by incorporating stability-enhancing modified nucleotides into the aptamer sequence during the synthesis stage, before the aptamer undergoes selection and binding assays. This pre-modification approach allows the stable structure to form correctly during the selection process, ensuring that the final aptamer maintains both high stability and high binding affinity without requiring post-selection structural adjustments that could compromise function.
Data Source
AI summary
Described are methods for utilizing X-aptamers for detecting human SNAP25 and fragments thereof, and compositions comprising the X-aptamers.