An innovative trimetallic-MOF mediated catalytic cleavage activity of FAM tagged Ag10/T-rich DNAzyme as an ultra-sensitive and selective fluorescent biosensor for subsequent recognition of Ag+ and Hg2+ ions

In this work, specific and sensitive recognition of the dual metal ions (Ag+ & Hg2+) through the FAM tagged Ag10/T-rich DNAzyme mediated Trimetallic-MOF (Ni/Zn with K-3[Co (CN)(6)]) as a biochemical sensing platform. Interestingly, the fluorescence probe of the FAM tagged specific Ag10/T-rich DNAzyme, and the Trimetallic-MOF demonstrated excellent analytical response towards subsequent recognition of the Ag+ & Hg2+ ions compared to the other coexisting targets. More precisely, the silver enzyme oligomer (EO) and FAM tagged thymine rich substrate oligomer (SO) were hybridized to form the Ag10/T-rich DNAzyme structure. When the Ag+ ion is induced into the Trimetallic-MOF with the FAM tagged Ag10/T-rich DNAzyme complex caused higher efficient internal catalytic cleavage at RNA site of FAM tagged substrate oligomer (SO). The released FAM tagged T-rich SO sequence was adsorbed on the Trimetallic-MOF surface through pi-pi stacking and electrostatic interactions, which diminished (Turn-OFF) the fluorescent signal. Surprisingly, the subsequent addition of the Hg2+ ions into the above-quenched system (Trimetallic-MOF/cleaved FAM tagged SO, and EO with Ag+) resulted in an enhancement of the fluorescence intensity (Turn-ON) due to the creation of the double-strand structure (T-Hg2+- T). By utilizing this sensor, susceptible and discriminating recognition of the Ag+ and Hg2+ ions is attained through the subsequent processes of catalytic cleavage of the DNAzyme and the FRET mechanism. As a result, the proposed biosensor achieved low detection limits of Ag+ (0.29 nM) and Hg2+ (0.10 nM), respectively. The utility of the developed fluorescence biosensor was established due to the subsequent recognition of the Ag+ and Hg2+ in actual water samples with satisfactory regaining and good reproducibility.

Automated summary

In this study, a biochemical sensing platform was developed using a fluorescent probe and a Trimetallic-MOF for specific and sensitive recognition of Ag+ and Hg2+ ions. The detection was achieved through catalytic cleavage of DNAzyme and the FRET mechanism, resulting in low detection limits and satisfactory recovery in water samples.