A G-quadruplex based fluorescent oligonucleotide turn-on probe towards iodides detection in real samples

Area of Science:

• Analytical Chemistry
• Biochemistry
• Molecular Biology

Background:

• G-quadruplex (GQ) structures are unique nucleic acid motifs with potential in biosensing.
• Mercury(II) ions (Hg2+) can mediate specific base-pair interactions, influencing probe design.
• Fluorescent oligonucleotide (OND) probes offer sensitive detection methods.

Purpose of the Study:

• To develop a novel fluorescent turn-on sensor for sensitive iodide anion detection.
• To utilize the interplay between G-quadruplex structures, thymine-Hg(II)-thymine (T-Hg(II)-T) base pairs, and fluorescence quenching for sensing.
• To validate the probe's performance in diverse sample matrices.

Main Methods:

• Design of a basket-type G-quadruplex fluorescent oligonucleotide probe.
• Exploitation of photoinduced electron transfer (PET) for fluorescence quenching.
• Utilizing the displacement of Hg2+ by iodide ions to trigger fluorescence recovery.
• Calibration and validation using fluorescence spectroscopy.

Main Results:

• The probe exhibited fluorescence quenching in the presence of Hg2+ due to PET.
• Addition of iodide ions caused fluorescence recovery by extracting Hg2+ from T-Hg(II)-T complexes.
• A linear detection range of 20-200 nmol/L for iodide was established.
• A low limit of detection (LOD) of 5 nmol/L for iodide was achieved.

Conclusions:

• A highly sensitive and selective fluorescent turn-on sensor for iodide detection was successfully developed.
• The probe demonstrated practical applicability for iodide determination in water, food, pharmaceutical, and biological samples.
• This approach offers a promising method for environmental and biological monitoring of iodide.