A Luminescent Cocaine Detection Platform Using a Split G-Quadruplex-Selective Iridium(III) Complex and a Three-Way...

Area of Science:

• Biochemistry
• Analytical Chemistry
• Materials Science

Background:

• G-quadruplexes are unique nucleic acid structures with potential in biosensing.
• Cyclometalated iridium(III) complexes offer tunable photophysical properties for luminescence-based detection.
• Developing selective and sensitive methods for cocaine detection remains a significant challenge.

Purpose of the Study:

• To design and synthesize a label-free, switch-on sensing platform for cocaine detection.
• To utilize a three-way DNA junction incorporating a G-quadruplex motif as a signal output unit.
• To screen cyclometalated iridium(III) complexes for selective binding to G-quadruplexes.

Main Methods:

• Synthesis and characterization of 10 in-house cyclometalated iridium(III) complexes.
• Screening of complexes for selectivity towards split G-quadruplex structures.
• Development of a luminescence-based assay using a three-way DNA junction architecture.
• Optimization of the sensing assay for cocaine detection and quantification.

Main Results:

• Iridium(III) complex 7 demonstrated excellent selectivity for the intermolecular G-quadruplex motif.
• A sensitive, label-free, switch-on cocaine detection method was established.
• The sensing approach achieved a low detection limit of 30 nM for cocaine.
• A linear correlation between luminescence intensity and cocaine concentration (30–300 nM) was observed.
• Successful detection of cocaine in diluted oral fluid samples was demonstrated.

Conclusions:

• A novel, highly selective, and sensitive label-free sensing platform for cocaine detection was successfully developed.
• The three-way DNA junction architecture combined with iridium(III) complex 7 offers a promising approach for bioanalytical applications.
• This oligonucleotide-based sensing method provides a valuable tool for cocaine detection in complex biological matrices.