L-DNA Comparator for Single Nucleotide Variation Detection
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Solution Overview
Problem
Current methods for detecting infectious diseases, such as tuberculosis, in resource-constrained settings are hindered by the lack of simple and cost-effective techniques for identifying sequence differences in nucleic acid amplification products, particularly for distinguishing between drug-susceptible and resistant strains, which delays effective treatment.
Innovation Solution
The use of L-DNA molecules with identical stereochemistry to a reference D-DNA sequence for detecting sequence variations by obtaining and comparing melt curves, allowing for the identification of differences through intercalating dyes or fluorescence-quencher pairs, and the inclusion of L-DNA in PCR reactions as a comparator to simplify reagent design and enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If culture methods are used to detect and characterize infectious disease strains, then accurate identification of drug resistance can be achieved, but the detection process takes weeks to months which delays treatment
Solution Approach 1:
The invention changes the detection parameter from cultural growth (weeks to months) to thermal melting temperature (Tm) differences that can be measured in real-time during PCR. By monitoring the Tm of PCR amplicons, the method achieves rapid detection of sequence variations including single nucleotide changes that confer drug resistance, reducing detection time from weeks/months to hours while maintaining identification accuracy
Solution Approach 2:
The invention replaces the mechanical/biological culture system with a thermal-based detection system. Instead of relying on bacterial growth and cultural characteristics, the method uses temperature-dependent DNA denaturation (melting) to detect sequence variations. This substitution enables rapid detection without requiring lengthy cultural growth periods
2Measurement precision
If melt analysis is used to detect sequence differences with calibrated instrumentation, then detection sensitivity can be improved, but device complexity and cost increase making it unavailable in resource-constrained settings
Solution Approach 1:
The invention uses the PCR amplicon itself as the detection target rather than requiring separate probe hybridization or complex probe designs. By analyzing the melting behavior of the amplified product directly, the method achieves high detection sensitivity for single nucleotide variations without requiring calibrated instrumentation or complex reagent designs, making it suitable for resource-constrained settings
Solution Approach 2:
The PCR amplicon serves its dual function as both the amplification product and the detection target. The sequence variations that differentiate drug-resistant strains are directly detected through their effect on the amplicon's melting temperature, eliminating the need for separate detection reagents or complex instrumentation. The system uses itself for detection, reducing complexity while maintaining sensitivity
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 enables the detection of subtle sequence changes, including single nucleotide substitutions, in a cost-effective manner, improving the classification of drug-susceptible and resistant strains, and can be adapted for other diagnostic scenarios where sequence differences impact treatment decisions.
Implementation Method 1
The L-DNA sequence and the test D-DNA sequence may be detected using an intercalating dye and/or a dye/quencher pair or by hyperchromicity
Implementation Method 2
The intercalating dye may be selected from the group consisting of SYBR® Gold, SYBR® Green, EvaGreen, SYTO 82, SYTO 64, SYTO 9, and LCGreen dyes
Implementation Method 3
Obtaining a melt curve may comprise heat separation of said L-DNA and/or said test D-DNA sequence
Implementation Method 4
Obtaining a melt curve for said L-DNA sequence; obtaining a melt curve for said test D-DNA sequence under conditions identical to step (b)
Data Source
AI summary
Variation in a single nucleotide of a target or template nucleic acid may be significant in many ways. For infectious disease, many drug resistance mutations are known and a simple means to confirm their absence would more quickly match a patient with an infection with the most effective treatment. This disclosure provides for a simple, low resource strategy allowing the detection of single nucleotide variation using only low-cost diagnostic methods already available in many locations. A key to this approach is the use of left-handed DNA (L-DNA) as a comparator molecule for D-DNA targets. L-DNA provides numerous additional advantages such as low cost and stability.