Plasmonic Nanoprobe Methylation Detection via Bisulfite PCR
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Solution Overview
Problem
Current methods for detecting DNA methylation, particularly in rare circulating tumor DNA, face challenges in distinguishing aberrant epigenetic changes from a large background of normal DNA, requiring highly sensitive and specific detection techniques.
Innovation Solution
A method involving bisulfite treatment, methylation-specific PCR, and plasmonic nanoprobe-based detection using gold nanoparticles and morpholino oligonucleotide probes to determine methylation status by analyzing melting temperature and color changes, with specific primers and blockers to enhance specificity and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methylation detection methods are used, then the detection process is simple, but the sensitivity and specificity are insufficient to distinguish rare methylated DNA from large background of normal DNA
Solution Approach 1:
The detection process is divided into distinct functional stages: bisulfite conversion step to differentiate methylated vs unmethylated cytosines, PCR amplification step to exponentially amplify only methylated sequences, and nanoprobe detection step to specifically detect the amplified methylated DNA. This segmentation allows each step to be optimized for its specific function, achieving high sensitivity and specificity while maintaining manageable complexity.
Solution Approach 2:
The bisulfite treatment is performed as a preliminary action before PCR amplification to convert unmethylated cytosines to uracils. This preliminary chemical modification creates a permanent distinction between methylated and unmethylated sequences, enabling subsequent specific amplification and detection of only methylated DNA, thereby achieving high measurement precision.
2Measurement precision
If highly sensitive detection methods are used to detect rare methylated DNA, then detection precision improves, but the complexity of the detection process increases
Solution Approach 1:
Bisulfite treatment is performed as a preliminary action to convert unmethylated cytosines to uracils, creating a permanent chemical distinction. This preliminary modification enables subsequent PCR amplification to specifically target and amplify only methylated sequences, achieving high sensitivity without requiring complex detection mechanisms.
Solution Approach 2:
The methylation status information is copied and amplified through PCR amplification of the methylated sequences. By creating multiple copies of the methylated DNA fragments, the method transforms the detection of rare single-molecule methylated sequences into the detection of abundant amplified products, significantly enhancing sensitivity while using standard PCR technology rather than complex specialized equipment.
3Measurement precision
If methylation-specific primers and blockers are used to enhance specificity, then the ability to distinguish methylated from unmethylated DNA improves, but the complexity of the PCR protocol increases
Solution Approach 1:
Methylation-specific primers are designed to bind specifically to sequences created by bisulfite conversion of methylated cytosines (which become thymines), while blocker sequences are designed to bind to unmethylated regions. This local quality differentiation allows the primers and blockers to selectively amplify only methylated sequences, achieving high accuracy in methylation status differentiation using standard PCR chemistry.
Solution Approach 2:
The blocker sequence acts as an intermediary element that binds to unmethylated DNA regions and prevents primer extension. This intermediary mechanism provides an additional layer of specificity control, ensuring that only properly methylated sequences are amplified, thereby enhancing differentiation accuracy without requiring multiple separate PCR reactions.
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 accurate detection of methylation status, including 0.01% methylated DNA in an unmethylated background, demonstrating high sensitivity and specificity suitable for colorectal cancer screening using cell-free DNA.
Implementation Method 1
bisulfite treatment of the sample for converting the unmethylated cytosine bases in the target nucleic acid molecule to uracil
Implementation Method 2
contacting the amplicons with a methylation-specific plasmonic nanoprobe comprising a plasmonic nanoparticle and a non-ionic oligonucleotide analog probe covalently coupled thereto, the oligonucleotide analog probe comprising a base sequence that is complementary to the target region, under conditions that allow the oligonucleotide analog probe and the amplicons comprising the target region to hybridize to each other
Implementation Method 3
determining the methylation status of the target nucleic acid molecule based on the determination of the melting temperature Tm of the hybrid of the nanoprobe and the target nucleic acid
Data Source
AI summary
The invention relates to methods and kits for determining the methylation status of a target nucleic acid molecule in a sample comprising (a) bisulfite treatment of the target nucleic acid, (b) amplifying the treated target nucleic acid with methylation-specific primers, (c) contacting the amplicons with a methylation-specific plasmonic nanoprobe and (d) determining the methylation status based on melting temperature Tm of the hybrid probe and the target nucleic acid. In particular, a plasmonic gold nanoparticle covalently coupled to a morpholino oligonucleotide probe. Also claimed are methods and kits for determining methylation status of the Septin 9 (SEPT9) gene promoter.