A DNA-based biosensor for aqueous Hg(II): Performance under variable pH, temperature and competing ligand...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Biotechnology

Background:

• Mercury (Hg) is a toxic metal with significant environmental and health risks.
• Accurate monitoring of Hg in aquatic systems is challenging due to limitations in current analytical techniques.
• Developing sensitive, selective, and field-deployable Hg sensors is crucial for environmental assessment.

Purpose of the Study:

• To evaluate a novel Hg²⁺ sensor based on the selective binding of Hg²⁺ to thymine-rich DNA.
• To assess the sensor's performance and reliability under various environmentally relevant conditions.
• To investigate and mitigate interferences affecting the sensor's accuracy.

Main Methods:

• Utilized a Hg²⁺ sensor employing thymine-rich DNA and SYBR Green I for fluorescence detection.
• Immobilized the DNA within a polyacrylamide hydrogel to enhance selectivity and reduce interferences.
• Employed equilibrium speciation calculations to account for complexation and validate sensor performance across diverse conditions.

Main Results:

• DNA-SYBR Green I interactions were sensitive to pH, metal ligands, and natural dissolved organic matter (NDOM).
• DNA immobilization in hydrogel largely eliminated interferences, though high NDOM concentrations posed challenges.
• Equilibrium speciation calculations accurately reproduced experimental results, including Hg²⁺ binding constants, across varied conditions.

Conclusions:

• The DNA-hydrogel based Hg²⁺ sensor demonstrates reliable performance for detecting mercury in aquatic environments.
• The developed method effectively minimizes common interferences, enhancing the potential for field deployment.
• Equilibrium speciation modeling provides a robust framework for understanding and correcting for complex matrix effects in mercury sensing.