Substituted Primers for Reliable Isothermal DNA Amplification
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Solution Overview
Problem
Isothermal nucleic acid amplification methods, such as RPA, often fail to consistently amplify specific DNA or RNA sequences and struggle with multiplexing, with unclear explanations for variable results, leading to unreliable procedures.
Innovation Solution
The use of substituted primers with analogs of A, T, G, and C nucleobases, such as 2-aminopurine, inosine, 2-thiothymine, and N4-ethylcytosine, and oligonucleotides from the artificially expanded genetic information system (AEGIS), which are compatible with the standard recombinase polymerase assay (RPA), enabling effective isothermal amplification of target nucleotides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard RPA methods are used for isothermal amplification, then the process maintains simple temperature control, but amplification reliability and consistency deteriorate due to sequence-dependent failures and multiplexing issues
Solution Approach 1:
The patent applies parameter changes by substituting standard nucleobases (A, T, G, C) with analogs (2-aminopurine, 2-thiothymine, inosine, N4-ethylcytosine) in the primer molecules. This chemical parameter modification of the primer structure enables consistent isothermal amplification across diverse target sequences and facilitates multiplexing, directly resolving the reliability issue while maintaining the isothermal condition advantage
Solution Approach 2:
The patent employs composite materials by creating primers that combine standard nucleotide backbones with non-standard nucleobase analogs. These hybrid primer structures integrate the stability of standard nucleotides with the enhanced binding properties of analogs, achieving both reliable amplification and reduced artifacts without compromising the isothermal process simplicity
2Reliability
If standard primers are used in RPA, then the procedure remains simple, but amplification consistency across different target sequences deteriorates
Solution Approach 1:
The patent modifies the chemical parameters of primers by incorporating nucleobase analogs during synthesis. This parameter change approach maintains relative ease of manufacture through standard oligonucleotide synthesis chemistry while dramatically improving amplification consistency across different target sequences, including viral targets like influenza and HIV
3Reliability
If standard RPA primers are used for multiplexing, then the system maintains simplicity, but amplification success rate deteriorates due to primer-primer interactions
Solution Approach 1:
The patent applies parameter changes to primer chemistry by substituting nucleobases with analogs that reduce non-specific interactions. This chemical modification enables successful multiplexing of multiple target sequences simultaneously by preventing primer-primer artifacts while maintaining the relative simplicity of the isothermal RPA framework
Solution Approach 2:
The patent effectively uses disposable substituted primers for each multiplexing application. These specialized primers with nucleobase analogs are designed for specific multiplexing tasks and can be synthesized on-demand, enabling reliable multi-target detection without requiring complex reusable system components
4Ease of operation
If standard primers are used in isothermal amplification, then the process remains straightforward, but artifacts from non-Watson Crick interactions increase
Solution Approach 1:
The patent modifies the chemical parameters of primers by incorporating nucleobase analogs that enforce more specific base pairing. This parameter change reduces non-Watson Crick interactions and artifacts during isothermal amplification, improving amplification purity and clarity while maintaining the straightforward single-temperature operation characteristic of RPA
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
These substituted primers and AEGIS oligonucleotides facilitate reliable isothermal amplification of DNA sequences, including viral targets like influenza and HIV, with clear product visualization and reduced artifacts, enhancing the robustness of isothermal amplification processes.
Implementation Method 1
enzymes that work in the standard recombinase polymerase assay (RPA) known in the art
Implementation Method 2
methods that amplify nucleic acids without the need to do temperature cycling
Implementation Method 3
Isothermal amplification methods frequently do not perform well, however
Implementation Method 4
primers ('substituted primers') in which at least some of the A, T, G, and C nucleobases are substituted at some ( but not necessarily all) sites (positions) with analogs designated A*, T*, G* and C*
Implementation Method 5
RPA-like processes where its substituted primers are tagged with oligonucleotides incorporating nucleotides selected from as artificially expanded genetic information system (AEGIS, herein defined) also perform well
Data Source
AI summary
This invention covers methods for isothermal amplification of DNA. It is based on the unexpected discovery that primers having, at some positions, adenine substituted by 2-aminopurine or diaminopurine, guanine by inosine, thymine by 2-thiothymine, and cytosine by N4-ethylcytosine (“substituted primers”) were accepted by enzymes used in the standard recombinase polymerase assay (RPA). Further unexpected was the discovery that target nucleotides are efficiently amplified in an RPA-like process (hereinafter abbreviated as simply RPA) using substituted primers. RPA-like processes were also discovered to amplify target DNA with substituted primers tagged with oligonucleotides incorporating nucleotides from an artificially expanded genetic information system (AEGIS).