Cooperative Binding Split Aptamers for Small Molecule Detection
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Solution Overview
Problem
Current aptamer-based sensors face challenges in achieving sensitive and specific detection of small-molecule targets, particularly due to high equilibrium dissociation constants and pre-assembly issues in split aptamers, which limit their effectiveness in detecting small-molecule-binding events at low concentrations.
Innovation Solution
The development of cooperative binding split aptamers (CBSAs) with two target-binding domains and a duplexed C3 spacer abasic site, which facilitates target-induced assembly and enzymatic signal amplification through exonuclease III activity, enabling sensitive and specific detection of small molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional split aptamers with a single binding domain are used, then the sensor can be assembled from separate fragments, but the equilibrium dissociation constant remains in the high micromolar range resulting in no measurable target-induced assembly
Solution Approach 1:
The aptamer is divided into two separate fragments that only assemble when bound to the target molecule. This segmentation allows the aptamer to remain inactive (low affinity) in the absence of target while achieving high affinity upon target binding, thereby improving measurement precision without requiring complex engineered structures.
Solution Approach 2:
Two aptamer fragments are combined through target-induced assembly to form a complete high-affinity binding site. The merging of fragments occurs only in the presence of the target, converting low-affinity separate components into a high-affinity complex, thus resolving the contradiction between structural simplicity and detection sensitivity.
2Strength
If split aptamers with longer complementary stems are engineered to improve target affinity, then binding strength increases, but pre-assembly occurs in the absence of target producing high background signal
Solution Approach 1:
The aptamer fragments are pre-designed with complementary stems that enable spontaneous assembly only when the target is present. The preliminary structural design ensures that high-affinity binding occurs only under the correct conditions (target presence), preventing premature assembly and background signal generation while maintaining strong target affinity.
Solution Approach 2:
The complementary stems are positioned locally within the aptamer fragments to create assembly-prone regions that only interact when the target is bound. This local quality enhancement ensures that high affinity is achieved at the target-binding interface without causing global pre-assembly, thereby increasing target affinity while minimizing background signal.
3Reliability
If aptamer-target binding forms complex tertiary structures, then specific recognition is achieved, but the structures become non-ideal substrates for nucleases reducing EATR efficiency
Solution Approach 1:
The aptamer is segmented into fragments that assemble around the target, creating a structured complex that maintains nuclease accessibility. The segmentation allows the formation of specific tertiary structures for target recognition while preserving regions that remain accessible to nucleases, thereby maintaining both target specificity and EATR amplification efficiency.
Solution Approach 2:
The target molecule acts as an intermediary that facilitates aptamer assembly into a structure that is both specific and nuclease-accessible. The target-mediated assembly creates a unique architecture where the aptamer fragments are positioned to recognize the target specifically while leaving the phosphodiester backbone accessible to exonuclease III for efficient signal amplification.
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
CBSAs significantly enhance target response and sensitivity, allowing for the detection of small molecules at very low concentrations with reduced background signal, making them suitable for both clinical and field applications.
Implementation Method 1
this approach relies on selective, nuclease-mediated degradation of the probe strand of a target-probe duplex that only forms in the presence of the target
Implementation Method 2
which facilitates target-induced assembly and enzymatic signal amplification through exonuclease III activity
Data Source
AI summary
The subject invention provides methods, assays and products for detecting small-molecules in a sample, in particular, in both clinical and field settings. The method for detecting a small-molecule target in a sample comprises providing a sample, contacting the sample with an aptamer-based sensor selective for the small-molecule target, and sensitively and rapidly detecting the small-molecule target in the sample. Specifically, the method utilizes EATR-amplified small-molecule sensors based on cooperative binding split aptamers (CBSAs).