Combining G-Quadruplex and Non-Quadruplex Aptamers with Distinct Thermodynamic Driving Forces for Highly Selective...

Area of Science:

• Nucleic acid chemistry
• Biotechnology
• Environmental science

Background:

• Lead ions (Pb²⁺) are significant environmental contaminants.
• DNA aptamers and G-quadruplex (G4) structures are explored for Pb²⁺ recognition.
• Understanding diverse Pb²⁺ binding mechanisms is crucial for developing advanced sensors.

Purpose of the Study:

• To select and characterize novel DNA aptamers for Pb²⁺ binding and detection.
• To elucidate the thermodynamic and structural basis of Pb²⁺-aptamer interactions.
• To develop a sensitive and selective sensor for Pb²⁺ detection.

Main Methods:

• Aptamer selection using low Pb²⁺ concentration and extended incubation.
• Isothermal Titration Calorimetry (ITC) for thermodynamic analysis.
• Development of a strand-displacement fluorescence sensor and Thioflavin T (ThT) fluorescence assays.

Main Results:

• Two distinct families of Pb²⁺-binding aptamers (Pb-13 and Pb-2-T) were identified.
• Aptamers exhibited diverse binding mechanisms: enthalpic, entropic, or hybrid G-quadruplex formation.
• A Pb-13 based sensor achieved a 7.5 nM detection limit for Pb²⁺.
• Opposite fluorescence responses (signal-off/on) enabled selective, label-free detection.

Conclusions:

• DNA aptamers can recognize Pb²⁺ via multiple, orthogonal structural and thermodynamic pathways.
• This work expands the understanding of metal ion recognition by nucleic acids.
• Developed aptamers and sensing strategies offer potential for environmental monitoring and diagnostics.