High Catalytic Activity of Fluorophore-Labeled Y-Shaped DNAzyme/3D MOF-MoS2NBs as a Versatile Biosensing Platform for the Simultaneous Detection of Hg2+, Ni2+, and Ag+ Ions

In this study, we have designed a three-fluorophore-labeled Y-shaped DNAzyme with a high catalytic cleavage activity and a three-dimensional (3D) MOF-MoS2NB (metal-organic framework fused with molybdenum disulfide nanobox), which was synthesized as an efficient quencher of the fluorescent biosensor. The synthesized porous 3D MOF-MoS(2)NBs and Y-shaped DNAzyme exhibited a good analytical response toward the simultaneous multiple detections of Hg2+, Ni2+, and Ag+ ions over the other coexisting metal ions. More specifically, the three kinds of enzyme aptamer and substrate aptamer (SA) were hybridized and annealed to form the Y-shaped DNAzyme structure and labeled with three different fluorophores such as FAM, TAMRA, and ROX over the 3'-end of SA. When the targets were induced, the DNAzyme was triggered to cleave the fluorophore-labeled SAs. Then, the cleaved SAs (FAM-SA, TAMRA-SA, and ROX-SA) were adsorbed on the 3D MOF-MoS2NB surface to quench the fluorescence signal due to a noncovalent interaction (van der Waals and pi-pi stacking interaction), which transmuted the fluorescence on-state to off-state. As a result, the fluorescence assay confiscated the high selectivity and sensitivity for the target analytes of Hg2+, Ni2+, and Ag+ ions achieved for the detection limits of 0.11 nM, 7.8 mu M, and 0.25 nM, respectively. Accordingly, the sensitivity of the developed sensor was explored with a better lower detection limit than the previously reported biosensors. The utility of the designed Y-shaped DNAzyme may find a broad field of application in real water sample analysis with interfering contaminants.

Automated summary

The study developed a three-fluorophore-labeled Y-shaped DNAzyme combined with a 3D MOF-MoS2NB for highly selective detection of Hg2+, Ni2+, and Ag+ ions, achieving detection limits of 0.11 nM, 7.8 μM, and 0.25 nM, respectively. The sensor showed improved sensitivity compared to previous biosensors and has potential applications in real water sample analysis with interfering contaminants.