Homogeneous amplified single-molecule detection: Characterization of key parameters

Area of Science:

• Molecular Biology
• Biotechnology
• Analytical Chemistry

Background:

• Single-molecule enumeration is vital for biological and diagnostic applications.
• Existing methods face challenges in sensitivity and precision.
• A novel approach transforms molecular recognition events into detectable DNA structures.

Purpose of the Study:

• To optimize a single-molecule enumeration method.
• To enhance precision and signal-to-noise ratio in microfluidic quantification.
• To investigate factors affecting rolling circle product (RCP) detection.

Main Methods:

• Utilizing target-specific padlock probe ligation and rolling circle amplification (RCA) for signal amplification.
• Employing microfluidic channels for sample handling and fluorescence microscopy for detection.
• Investigating the impact of confocal volume, RCP aggregation, and detection site density on quantification.

Main Results:

• High-precision microfluidic quantification achieved with optimized confocal volume (CV typically 3%).
• Complementary sequence motifs in RCPs showed minimal aggregation.
• Detection site saturation occurred above 5 nM detection oligonucleotide concentration.
• Increasing RCP detection site density by 1.9-fold boosted signal/noise from 42 to 75.

Conclusions:

• Confocal volume definition is critical for accurate microfluidic single-molecule quantification.
• RCP aggregation is not a significant issue under tested conditions.
• Signal-to-noise ratio is primarily limited by the number of detection sites on RCPs.
• Enhanced detection site density offers a direct route to improved optical signal and assay sensitivity.