AND-Logic Cascade Rolling Circle Amplification for Optomagnetic Detection of Dual Target SARS-CoV-2 Sequences

Area of Science:

• Molecular Biology
• Biosensing
• Nanotechnology

Background:

• DNA logic operations are valuable for multiplexing and diagnostics but often suffer from high detection limits.
• Existing assays typically lack pre-amplification, restricting sensitivity to subpicomolar to nanomolar levels.

Purpose of the Study:

• To develop a homogeneous, isothermal AND-logic cascade amplification strategy for optomagnetic biosensing.
• To enhance the detection limits of DNA logic operations for SARS-CoV-2 variant detection.

Main Methods:

• An "amplifiers-before-operator" configuration using padlock probes for dual DNA input recognition and cascade amplification.
• Secondary amplification generates products that interact with magnetic nanoparticles (MNPs).
• Real-time optomagnetic MNP analysis measures hydrodynamic size changes and aggregation.

Main Results:

• Achieved an ultra-low detection limit of 8.6 fM for specific DNA sequences.
• Demonstrated a dynamic detection range exceeding 3 orders of magnitude.
• Validated accuracy, stability, and specificity using complex biological samples and clinical specimens.

Conclusions:

• The developed AND-logic cascade amplification strategy significantly enhances sensitivity in DNA-based biosensing.
• This method offers a powerful tool for accurate and sensitive detection of viral variants and other targets.
• The optomagnetic MNP analysis provides a robust platform for intelligent diagnostics with high consistency.