Y-switch: a spring-loaded synthetic gene switch for robust DNA/RNA signal amplification and detection

Area of Science:

• Synthetic biology
• Molecular diagnostics
• Biomolecular engineering

Background:

• Traditional nucleic acid tests (NATs) are crucial but often complex and costly.
• Toehold-mediated strand displacement (TMSD) offers an economical alternative for NATs.
• TMSD reactions suffer from 'leakage,' causing high background and false positives, limiting their application.

Purpose of the Study:

• To introduce the Y-Switch, a novel TMSD cascade design for sensitive and specific nucleic acid detection.
• To overcome the limitations of leakage in TMSD-based assays.
• To develop a low-complexity, high-fidelity synthetic biology tool for point-of-care diagnostics.

Main Methods:

• Designed a Y-Switch cascade using spring-loaded DNA modules for custom nucleic acid recognition.
• Triggered an intermolecular reaction activating a T7 promoter for amplified fluorescent aptamer transcription.
• Incorporated selective depletion of leakage byproducts for zero-background signal.
• Validated the system using Zika virus (ZIKV) and SARS-CoV-2 RNA sequences.

Main Results:

• The Y-Switch assay demonstrated reliable, target-specific readouts for ZIKV and SARS-CoV-2 nucleic acids.
• Achieved high sensitivity with a detection threshold as low as ~200 attomole.
• Detected native RNA under isothermal conditions without reverse transcription or pre-amplification.
• Showcased modularity for easy re-programming to detect different targets.

Conclusions:

• The Y-Switch provides a sensitive, specific, and economical method for nucleic acid testing.
• The system effectively minimizes background noise and false positives inherent in TMSD reactions.
• Offers a versatile synthetic biology tool for point-of-care diagnostics and advanced biomolecular computations.