Silencing Oligonucleotide for Padlock Probe Specificity
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Solution Overview
Problem
Current methods for removing unhybridized padlock probes in nucleic acid detection assays are inefficient, particularly in homogenous solutions, and can lead to mis-priming and reduced specificity and sensitivity due to the presence of free padlock probes.
Innovation Solution
The use of a silencing oligonucleotide that hybridizes to the ends of padlock probes, preventing them from participating in further reactions by creating a gap that keeps the ends apart, ensuring the probes are functionally inactivated unless a correct template is present, allowing for RCA to be initiated only after the silencing oligonucleotide is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If free padlock probes are removed by washing or enzymatic digestion, then mis-priming is reduced, but the method requires additional steps (washing, solid phase, or enzyme inactivation) that reduce ease of operation
Solution Approach 1:
A silencing oligonucleotide is introduced as an intermediary substance that hybridizes to free padlock probes to prevent mis-priming. This mediator allows the system to achieve high specificity without requiring washing steps, solid phases, or enzyme inactivation, thereby maintaining ease of operation while improving reliability
Solution Approach 2:
The harmful function of free padlock probes (mis-priming) is extracted and neutralized by the silencing oligonucleotide, which specifically binds to and silences unligated probes. This separates the problematic free probes from the functional ligated probes without requiring physical removal steps
2Reliability
If exonuclease is used to digest free padlock probes, then specificity is improved, but the method requires additional expense and enzyme inactivation steps
Solution Approach 1:
The silencing oligonucleotide serves as a simple, inexpensive, single-use reagent that replaces expensive enzymes like exonuclease. It performs the function of selectively silencing free probes without requiring enzyme inactivation steps, reducing both cost and procedural complexity
Solution Approach 2:
The biochemical mechanism of enzymatic digestion by exonuclease is replaced with a simpler hybridization-based silencing mechanism. The silencing oligonucleotide uses base-pairing to neutralize free probes instead of requiring enzymatic activity, eliminating the need for enzyme addition and inactivation steps
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 assays by preventing non-specific reactions and improving signal detection, particularly in homogenous formats, without the need for additional enzymatic steps or solid phases.
Implementation Method 1
a silencing oligonucleotide which comprises first and second silencing regions which are complementary to the target-binding regions at the ends of the padlock probe
Implementation Method 2
RCA is commonly used for such amplification, and is typically used in conjunction with padlock probes. RCA utilises a strand displacement polymerase enzyme, and requires a circular amplification template
Implementation Method 3
the ends of the probe may be ligated together to circularise the probe
Data Source
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Figure 2A~2C
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AI summary
The present invention provides a method for detecting a target nucleic acid molecule in a sample, using padlock probes and rolling circle amplification. The method herein provides a new way of removing free padlock probes which have failed to hybridise to their target, or to be ligated, and involves the use of a "silencing" oligonucleotide to "block" such unbound, or unligated, padlock probes.