Nested Primer Sets for Exponential Nucleic Acid Amplification
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Solution Overview
Problem
Conventional PCR methods face limitations in amplification efficiency, with a less than two-fold increase in target sequence per cycle and sensitivity issues, making it difficult to detect targets present at low concentrations.
Innovation Solution
The use of novel primer sets, including outer and inner primers with specific sequences and clamp sequences, designed to enhance amplification efficiency by maintaining the outer primer binding site in amplicons and employing DNA polymerases with strand displacement activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional PCR methods are used, then the amplification process is simple and well-established, but the amplification efficiency is limited to less than two-fold increase per cycle and sensitivity is insufficient for detecting low-concentration targets
Solution Approach 1:
The primer set is segmented into outer primers and inner primers with distinct functions. Outer primers define the amplicon boundaries and maintain binding sites in products, while inner primers provide additional initiation sites within the amplicon. This segmentation enables multiple amplification pathways simultaneously, achieving greater than two-fold increase per cycle while maintaining manageable complexity through clear functional division.
Solution Approach 2:
The nested primer structure places inner primers within the region defined by outer primers. The inner primers bind to sequences nested within the outer primer binding sites, creating a hierarchical arrangement where inner primer amplicons are contained within outer primer amplicons. This nesting strategy multiplies the number of amplification templates generated each cycle, dramatically increasing amplification efficiency.
2Measurement precision
If conventional PCR with single primer pairs is used, then the reaction system is simple, but the sensitivity is limited and cannot detect targets present at only a few molecules
Solution Approach 1:
The primer design performs preliminary action by pre-positioning multiple primer binding sites (both outer and inner primers) that will generate amplification products containing preserved outer primer binding sites. This preliminary arrangement ensures that each cycle produces templates that can be re-used by the same primer set, creating a self-sustaining amplification system that rapidly increases target copy number even from single-molecule starting points.
Solution Approach 2:
The invention changes the fundamental parameter of amplification fold-increase from less than two-fold to greater than two-fold per cycle. This parameter change is achieved through the specific primer architecture where inner primers create additional templates while outer primers ensure template re-usability. The result is exponential acceleration of amplification, reducing the number of cycles needed to detect low-concentration targets.
3Measurement precision
If nested PCR is used to increase specificity and sensitivity, then the detection capability improves, but the amplification efficiency remains limited to less than two-fold increase per cycle
Solution Approach 1:
The primer set creates a dynamic amplification system where the relative contributions of outer and inner primers shift during the reaction. Early cycles are dominated by outer primer amplification establishing the amplicon framework, while subsequent cycles increasingly utilize inner primer sites within the accumulated amplicons. This dynamic progression allows the system to transition from establishing specificity to maximizing amplification rate, achieving both sensitivity and high productivity.
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
This approach allows for a sustained higher-fold increase in amplification per cycle, significantly reducing the number of amplification cycles required to detect single-copy nucleic acids, enhancing sensitivity and speed.
Implementation Method 1
the first outer primer including a primer sequence a that specifically hybridizes to first template strand sequence a′; and the first inner primer including a single-stranded primer sequence b that specifically hybridizes to first template strand sequence b′
Implementation Method 2
amplifying the target nucleic acid, if present, using a DNA polymerase lacking 5′-3′ exonuclease activity, under conditions where strand displacement occurs
Implementation Method 3
under conditions where strand displacement occurs, to produce amplicons that comprise sequence extending from template sequence a′ to the binding site for the second primer
Data Source
AI summary
Described herein are methods and compositions that provide highly efficient nucleic acid amplification. In some embodiments, this allows a greater than 2-fold increase of amplification product for each amplification cycle and therefore increased sensitivity and speed over conventional PCR.