Functional aptamers and aptazymes in biotechnology, diagnostics, and therapy

A comprehensive update of some of novel and promising developments of in vitro selection and aptamer, intramer, and allosteric ribozyme technology has been presented including the newly discovered natural aptamers, or riboswitches. Aptamer's flexibility is its main quality. Its nucleic acid allows synthetic access with convenient and versatile modification with functional groups. Therefore, they can be employed for various applications ranging from diagnostic to therapeutic assay formats. However, the fact that aptamers are negatively charged makes it difficult for use in therapeutic application for intracellular target proteins because they cannot easily cross cellular membranes. Regardless of its drawback, development in aptamers still shows feasibility in drug discovery process considering development in a wide range of delivery systems to facilitate intracellular delivery of therapeutic nucleic acids. In vitro selected aptamers that affect translation of reporter genes in cells preceded the discovery of similar-acting natural riboswitches. Engineered allosteric ribozymes regulated by small organic molecules antedated the recent discovery of the first catalytic riboswitch regulated by glucosamine-6-phosphate. By these developments, aptamers are considered as key players in opening new possibilities in the future.