DNAzymes: Synthetic Enzymes Made of DNA

The development of the “in vitro selection” technique in the early 1990s has led to the isolation of many DNAzymes—man-made single-stranded DNA molecules with catalytic abilities—from synthetic random-sequence DNA pools. This chapter serves to introduce this class of synthetic enzymes. Although DNAzymes have been derived to catalyze a diverse range of chemical reactions, we will exclusively focus on RNA-cleaving DNAzymes, the best studied class to date. RNA-cleaving DNAzymes refer to DNA molecules that catalyze sequence-specific cleavage of a phosphodiester bond located within an all-RNA or a chimeric RNA/DNA molecule. We will begin with a description of the in vitro selection method with which an RNA-cleaving DNAzyme can be derived. This will be followed by a discussion on a few well-studied RNA-cleaving DNAzymes, with a focus on their properties and their demonstrated applications. The last section of the chapter will be dedicated to our work in the area of selecting bacteria-responsive RNA-cleaving DNAzymes and applying them to design simple biosensors for bacterial pathogen detection.