Aptamers: Magic Bullet for Theranostic Applications

Aptamers are a short polymer of oligonucleotides (natural or modified) that can bind to its cognate target (small molecules to large macromolecules like proteins, cells, microorganisms etc.) with high affinity and selectivity. They can fold into unique secondary and tertiary conformation in solution (pH, ionic concentration) and bind to their targets in a specific manner (binding constants in sub-nano to pico molar range). They rival the monoclonal antibodies and other specific biological ligands with respect to affinity, stability, robustness, non-immunogenicity and facile to synthesis. Nucleic acid aptamers are selected from an oligonucleotide library by an iterative process called SELEX (Systematic Evolution of Ligands by Exponential Enrichment Analysis). These aptamers are compatible to any kind of chemical modification, conjugation and functionalization. Briefly, this chapter discusses about the diagnostic and therapeutic application of aptamers.