Applications of RNA-Cleaving DNAzymes

RNA-cleaving DNAzymes have found a variety of different applications. Selective targeting of mRNA in vivo, in order to suppress the expression of specific genes that cause disease, is an obvious field of application of deoxyribozymes. Efforts in this direction have been reviewed [57, 58], 

Since some DNAzymes depend on specific metal ions for activity, they can be employed for the detection of those ions, hi the first example, a previously reported [59] DNAzyme was labeled with a Dabcyl fluorescence quencher at the 3 -end and the corresponding RNA substrate with a TAMRA fluorophore at the 5 -end [60]. Upon addition of Pb ions, the substrate was cleaved, resulting in dissociation from the DNA enzyme strand. This led to spatial separation of the fluorophore-quencher pair, resulting in fluorescence (Fig. 5). The sensor system was over 80 times more responsive to Pb than to other metal ions, and had a quantifiable detection range of 10 nM to 4 pM. A similar strategy was developed for the detection of Ctf by a DNAzyme that oxidatively cleaves DNA [61]. The system showed a dynamic range of 35 nM to 20 pM and had a metal ion selectivity of a factor of 2000 for Cu over other metal ions. A comparable system was reported for the detection of the uranyl cation (UO/ ), with millionfold selectivity over other metal ions and parts-per-trillion sensitivity. 

A different approach to DNAzyme sensors relies on the visual properties of aggregated gold nanoparticles [62-64]. The substrate for the DNAzyme is designed so that 

In addition to chemical sensors, DNAzymes have found applications in molecular logic gates [68-70] and molecular motors [71, 72], 

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