Isothermal Nucleic Acid Detection Probe With 3' Mismatch
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Solution Overview
Problem
Current sequence-specific detection methods for nucleic acid amplification, particularly in isothermal amplification for COVID-19 detection, face challenges such as poor specificity, sensitivity, and ease of use, often resulting in false positives and requiring complex probe designs and expensive reagents.
Innovation Solution
A method utilizing a detection probe with a 3′ end nucleotide mismatch and a quencher-fluorophore pair, which hybridizes to target amplicons and is cleaved by DNA polymerase with 3′-5′ exonuclease activity, allowing for specific and sensitive detection of nucleic acid molecules without the need for extensive probe design or expensive reagents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sequence-independent detection methods are used to detect amplified products, then detection simplicity is improved, but specificity deteriorates due to false positives from primer dimers and nonspecific products
Solution Approach 1:
A detection probe with a 3' end nucleotide mismatch acts as an intermediary between the amplification reaction and the detection system. The probe hybridizes to the target amplicon and serves as a substrate for DNA polymerase with 3'-5' exonuclease activity, which cleaves the mismatched 3' end to generate a fluorescent signal. This intermediary mechanism ensures that only specific target amplicons trigger the signal, eliminating false positives from nonspecific amplification products.
Solution Approach 2:
The detection probe incorporates a 3' end nucleotide mismatch parameter that changes the substrate recognition properties. The mismatched nucleotide at the 3' end creates a specific recognition feature that DNA polymerase with 3'-5' exonuclease activity can identify and cleave. This parameter change enables the system to distinguish between specific and nonspecific amplification products, improving specificity while maintaining simple detection.
2Reliability
If complex probe designs are used to improve specificity, then reliability is improved, but ease of operation deteriorates due to extensive design requirements
Solution Approach 1:
The detection system is segmented into distinct functional components: a detection probe with a specific 3' end mismatch, DNA polymerase with 3'-5' exonuclease activity, and a fluorophore-quencher system. The probe itself is segmented with the quencher at one end and the fluorophore at the other, separated by a specific distance. This segmentation allows each component to perform its specific function independently, simplifying the overall design while maintaining high specificity.
Solution Approach 2:
The key parameter change is the 3' end nucleotide mismatch in the detection probe, which fundamentally simplifies the design requirements. Instead of requiring complex probe structures or multiple probes, the system relies on this single critical parameter - the mismatched nucleotide at the 3' end - which enables specific recognition and cleavage by the DNA polymerase. This parameter change makes the system both specific and easy to use.
3Measurement precision
If expensive reagents and instrumentation are used to improve detection accuracy, then measurement precision is improved, but cost increases
Solution Approach 1:
The detection system utilizes self-service mechanisms where the target amplicon itself serves as the template for probe hybridization, and the DNA polymerase with 3'-5' exonuclease activity present in the isothermal amplification reaction mixture serves as the cleavage enzyme. No additional expensive enzymes or separate detection instruments are required - the system uses components already present in the amplification reaction, thereby achieving high detection accuracy without increased cost.
Solution Approach 2:
The DNA polymerase with 3'-5' exonuclease activity performs multiple functions: it extends the detection probe during hybridization and then cleaves the mismatched 3' end to generate the fluorescent signal. The isothermal amplification reaction mixture serves dual purposes by both amplifying the target and providing the detection enzyme. This multi-functionality eliminates the need for separate expensive reagents and instrumentation, maintaining high measurement precision while controlling costs.
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 enhances the specificity and sensitivity of nucleic acid detection while being affordable and simple to use, reducing the risk of false positives and enabling rapid, decentralized testing for COVID-19 and other pathogens.
Implementation Method 1
a detection probe with a 3′ end nucleotide mismatch and a quencher-fluorophore pair
Implementation Method 2
a quencher-fluorophore pair at opposite ends of the probe at a distance that allow the quencher to quench the fluorophore signal
Implementation Method 3
cleavage of the detection probe at the 3′ end nucleotide mismatch by the DNA polymerase with 3′-5′ exonuclease activity
Implementation Method 4
the detection probe can hybridize to said target amplicons under isothermal amplification assay conditions except for the 3′ end nucleotide mismatch and form a double-stranded probe:target complex
Implementation Method 5
amplifying the target nucleic acid molecule under isothermal amplification assay conditions that allow generation of the target amplicons
Data Source
AI summary
Various embodiments relate generally to the field of nucleic acid amplification and detection, in particular isothermal nucleic acid amplification and the detection of the amplicons using designated detection probes. Moreover, various embodiments also relate to methods for determining the presence or quantity of a target nucleic acid molecule in a sample using isothermal amplification. The detection probe is a single-stranded probe that recognises a probe binding site within target amplicons. The detection probe comprises at least one 3′end nucleotide mismatch and a quencher-fluorophore pair at the opposite ends of the probe. Following hybridization of the detection probe to the target amplicons, a DNA polymerase with 3′-5′ exonuclease activity can cleave the detection probe at the 3′ end nucleotide mismatch to release a 3′-terminal probe fragment comprising the quencher or fluorophore, thus generating signals.