Cleavable Molecular Beacon for Hg(2+) Detection Based on Phosphorothioate RNA Modifications.

Area of Science:

• Biochemistry
• Environmental Science
• Nanotechnology

Background:

• Mercury (Hg(2+)) is a toxic heavy metal with significant environmental and health implications.
• Existing DNA-based biosensors for Hg(2+) often have limitations related to buffer conditions or require DNA hybridization.
• There is a need for robust and sensitive Hg(2+) detection methods.

Purpose of the Study:

• To develop a new Hg(2+) detection mechanism using phosphorothioate (PS) modified RNA.
• To create a highly selective and sensitive Hg(2+) biosensor based on this mechanism.
• To evaluate the sensor's performance in real-world water samples.

Main Methods:

• Investigated the cleavage of phosphorothioate (PS) modified RNA induced by various metal ions, focusing on Hg(2+).
• Optimized reaction conditions (pH, temperature) for Hg(2+)-induced RNA cleavage.
• Designed and synthesized a molecular beacon incorporating PS RNA modifications for Hg(2+) detection.
• Tested the sensor's selectivity and sensitivity using standard solutions and a Lake Ontario water sample.

Main Results:

• Hg(2+) specifically induced significant cleavage (~16%) of PS modified RNA, while other metal ions showed minimal cleavage (<2%).
• The cleavage reaction was efficient across a broad pH range (3.5–7) and temperature range (20–90 °C).
• PS RNA junctions were cleaved, but PS DNA junctions were not, indicating high specificity.
• A molecular beacon sensor detected Hg(2+) down to 1.7 nM with excellent selectivity.
• The sensor successfully detected Hg(2+) in a natural water sample, though masked by fish tissues.

Conclusions:

• Hg(2+)-induced cleavage of PS modified RNA presents a novel and robust mechanism for biosensing.
• The developed molecular beacon offers a sensitive and selective platform for Hg(2+) detection.
• This approach overcomes limitations of existing DNA-based sensors and shows potential for environmental Hg(2+) monitoring.