Multi-part Primer Bubble Structure for Rare Target Detection
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Solution Overview
Problem
Current primer technologies face challenges in detecting and quantifying rare target sequences, such as mutant DNA, in the presence of abundant wild-type sequences, especially when the difference is as little as a single-nucleotide polymorphism, with existing methods having limited sensitivity and specificity.
Innovation Solution
A multi-part primer design consisting of an anchor sequence, a bridge sequence, and a foot sequence, where the bridge sequence is mismatched to the target, forming a bubble structure that delays amplification of unintended targets, allowing for selective amplification and detection of rare target sequences with high specificity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional primers are made sufficiently long to ensure specificity, then the primer anneals to only one place in the nucleic acid strand, but the selectivity for distinguishing rare target sequences from abundant wild-type sequences deteriorates
Solution Approach 1:
The primer is divided into three functional segments: an anchor sequence (104) that binds to the target, a bridge sequence (105) that forms a bubble structure with a blocking group to prevent extension of wild-type sequences, and a foot sequence (106) that provides selectivity through mismatched base pairing. This segmentation allows each part to perform its specific function, achieving both high specificity and selectivity simultaneously.
Solution Approach 2:
Different regions of the primer have different properties optimized for their specific functions. The anchor sequence has high complementarity for stable binding, the bridge sequence contains a blocking group at a specific location to prevent extension, and the foot sequence has deliberate mismatches to differentiate target from wild-type. This local differentiation of properties enables the primer to achieve both specificity and selectivity.
2Measurement precision
If the primer length is shortened to improve selectivity, then the selectivity for one allele over another improves, but the specificity deteriorates because short primers are unlikely to form stable hybrids at typical annealing temperatures
Solution Approach 1:
The primer is divided into three functional segments: an anchor sequence (104) that binds to the target, a bridge sequence (105) that forms a bubble structure with a blocking group to prevent extension of wild-type sequences, and a foot sequence (106) that provides selectivity through mismatched base pairing. This segmentation allows each part to perform its specific function, achieving both high specificity and selectivity simultaneously.
Solution Approach 2:
Different regions of the primer have different properties optimized for their specific functions. The anchor sequence has high complementarity for stable binding, the bridge sequence contains a blocking group at a specific location to prevent extension, and the foot sequence has deliberate mismatches to differentiate target from wild-type. This local differentiation of properties enables the primer to achieve both specificity and selectivity.
3Measurement precision
If ARMS primers are used to improve selectivity through mismatched 3'-terminal nucleotides, then the selectivity improves, but the detection limit remains at about 1% due to the refractory nature of DNA polymerases
Solution Approach 1:
The bridge sequence (105) contains a blocking group positioned to prevent DNA polymerase extension before the polymerase can act on the primer. This preliminary blocking action occurs at the bridge region, allowing the foot sequence to provide selectivity while the blocking group ensures that only perfectly matched targets are amplified, thereby lowering the detection limit below the conventional 1% threshold.
4Productivity
If conventional primers are used to amplify all variants, then all alleles are amplified, but the detection of rare alleles is overwhelmed by the prevalent allele due to limited sensitivity
Solution Approach 1:
The bridge sequence (105) contains a blocking group positioned to prevent DNA polymerase extension before the polymerase can act on the primer. This preliminary blocking action occurs at the bridge region, allowing the foot sequence to provide selectivity while the blocking group ensures that only perfectly matched targets are amplified, thereby lowering the detection limit below the conventional 1% threshold.
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 multi-part primer design significantly enhances the selectivity and sensitivity, enabling the detection of as few as 10 mutant sequences in a sample containing 1,000,000 wild-type sequences, with a delay in amplification cycles indicating the presence of rare targets, facilitating early detection of cancer cells and key mutations.
Implementation Method 1
the bridge sequence and its opposed intervening sequence in the target form a bubble
Implementation Method 2
The bridge sequence is mismatched to the target, forming a bubble structure
Data Source
AI summary
This invention discloses multi-part primers for primer-dependent nucleic acid amplification methods. Also disclosed are primer-dependent nucleic acid amplification reactions, particularly DNA amplification reactions, reaction mixtures and reagent kits for such reactions. This invention relates to primer-dependent nucleic acid amplification reactions, particularly DNA amplification relations such as PCR, and primers, reaction mixtures and reagent kits for such reactions and assays employing same.