A Self-immolative Molecular Beacon for Amplified Nucleic Acid Detection*

Area of Science:

• Molecular Biology
• Biochemistry
• Chemical Biology

Background:

• Fluorogenic hybridization probes typically offer limited sensitivity due to a one-target/one-probe activation ratio.
• Existing methods struggle to amplify signals effectively for low-abundance nucleic acid detection.

Purpose of the Study:

• To introduce a novel self-immolative molecular beacon (iMB) probe that overcomes the limitations of traditional probes.
• To develop a unimolecular probe system for enhanced sensitivity in nucleic acid detection.

Main Methods:

• Design of an iMB probe incorporating a photoreductively cleavable N-alkyl-picolinium (NAP) linkage.
• Utilizing a 5'-end fluorophore as both a reporter and a photosensitizer for NAP-linker cleavage.
• Employing a hairpin structure with quencher groups to prevent premature cleavage in the absence of a target.

Main Results:

• The iMB probe opens upon target hybridization, enabling both fluorescent emission and photo-reductive cleavage of the NAP linker.
• Cleavage products exhibit reduced target affinity, facilitating a cascade effect.
• The method successfully detected 5 picomolar (pM) RNA targets within 100 minutes, demonstrating significant sensitivity enhancement.

Conclusions:

• The self-immolative molecular beacon (iMB) represents a significant advancement in nucleic acid detection sensitivity.
• This unimolecular probe system offers a novel approach to chemical amplification, surpassing previous methods.
• The iMB technology holds promise for sensitive and efficient detection of RNA and DNA sequences.