Three-phase nested amplification for multiplex nucleic acid detection
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Solution Overview
Problem
Current methods for detecting target nucleic acids in multiplex nucleic acid amplification-based assays are inefficient in identifying drug-resistant tuberculosis strains, particularly XDR-TB, due to limitations in detecting multiple targets simultaneously in a single assay cartridge.
Innovation Solution
A method involving a three-phase, nested amplification scheme in a cartridge-based system, which includes preamplification, asymmetric or symmetric amplification with nested primers and target-specific probes, followed by melt analysis or real-time PCR for detection, enabling the simultaneous detection of multiple target nucleic acids, including those associated with drug resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple target nucleic acids are detected simultaneously in a single assay cartridge, then the ability to identify drug-resistant tuberculosis strains is improved, but the device complexity increases
Solution Approach 1:
The patent implements a nested amplification scheme where a first amplification reaction is contained within a second amplification reaction in the same reaction mixture. The outer primers amplify a broader target region while inner primers amplify a nested subset, allowing hierarchical detection of multiple targets including drug resistance markers without requiring separate reaction vessels or complex fluidic systems
Solution Approach 2:
The assay uses a universal outer primer set that can amplify multiple different target regions (e.g., IS6110, IS1081, and drug resistance genes) while maintaining a single reaction mixture composition. This multi-functional primer design allows one assay cartridge to detect various Mycobacterium tuberculosis strains and their resistance profiles simultaneously
2Productivity
If a three-phase nested amplification scheme is used, then the detection efficiency of multiple targets is improved, but the time to result increases
Solution Approach 1:
The patent performs a preamplification phase before the main nested amplification to generate sufficient initial amplicons from low-abundance targets. This preliminary enrichment step ensures that subsequent amplification phases can detect rare targets efficiently, improving overall sensitivity without requiring excessive cycling in the main reaction
Solution Approach 2:
The nested amplification scheme uses the same reaction mixture and enzyme system throughout all amplification phases, eliminating the need to stop, transfer, or reset between steps. The outer and inner primers amplify simultaneously in a continuous process, maintaining productive action throughout the entire reaction duration
3Measurement precision
If nested primers and target-specific probes are used, then the measurement precision of target detection is improved, but the device complexity increases
Solution Approach 1:
The patent employs target-specific probes with unique melting temperatures and fluorescent labels assigned to specific target sequences (e.g., different drug resistance genes). Each probe is optimized locally for its specific target, allowing precise differentiation of multiple targets through melt analysis or fluorescence detection while using a single reaction mixture
Solution Approach 2:
The nested primer system acts as an intermediary that selectively amplifies specific target regions from the complex genomic DNA. The inner primers bind to sequences within the outer primer amplicons, providing an additional layer of specificity that enriches the target of interest while reducing background from non-specific 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
This approach allows for the efficient detection of multiple target nucleic acids, including drug resistance markers, in a single assay cartridge, significantly improving the ability to identify XDR-TB strains and other organisms, while reducing the time to result.
Implementation Method 1
nucleic acid amplification
Implementation Method 2
target-specific probes
Implementation Method 3
DNA intercalating dye
Implementation Method 4
melt analysis
Data Source
AI summary
The present disclosure provides three-phase, nested amplification methods that facilitate multiplex amplification and multi-phasic detection, particularly multiplex amplification assays that employ target-specific melt probes and/or high-resolution melt (HRM) analysis using an intercalating dye.