Functional Nucleic Acids for Fluorescence-Based Biosensing Applications

Functional nucleic acids (FNAs) are single-stranded DNA or RNA molecules that are capable of carrying out the function of ligand binding (by aptamers), catalysis (by nucleic acid enzymes), or both (by aptazymes). Many FNAs have been shown to be suitable molecular recognition elements for many molecular targets, including small molecules and proteins, and have been examined for a variety of biosensing applications. In this chapter, we present a focused discussion on the use of FNAs for the development of fluorescence-based biosensors or bioassays. First, we briefly discuss the technique of “in vitro selection” by which artificial FNAs can be isolated from random-sequence DNA or RNA pools. This is followed by a survey of various strategies in employing aptamers for fluorescence assay development. Finally, we review emerging applications to explore nucleic acid enzymes (ribozymes, DNAzymes, and aptazymes) as fluorescent biosensing probes.