Aptamer: A Novel Therapeutic Oligonucleotide

Abstract

The aptamer is an oligonucleotide which is a short version of biological nucleic acids (such as DNA and RNA) with defined sequence of nucleotides. Based on the complexity of molecule, the aptamers lies in-between protein molecules and small chemical molecules. Aptamers have high specificity and affinity towards target proteins. They are screened from random sequences of oligonucleotides based on the highest affinity for target proteins using the SELEX (Systematic Evolution of Ligands by Exponential Enrichment). Researchers have discovered various applications of aptamers that are ready to replace the therapeutic use of biological proteins (such as antibodies) that have complexity in manufacturing and characterization. The present review describes the structural modification in aptamers such as PEGylation, substitution of functional groups, use of an enantiomeric oligonucleotide and its applications. Aptamers can be deactivated, when needed, by the use of reversal agent that contains oligonucleotide sequence complementary to aptamers. This property of aptamers makes them potential therapeutic from a safety point of view. In recent scenario, aptamers are developed for targeted drug delivery systems by conjugating with drug molecules or delivery vesicles such as liposomes. ' Anti-sense Aptamers' are being developed to silent the expression of genes responsible for the proliferative growth of tissue in cancer. Other applications of aptamers such as environmental monitoring and laboratory testing are also described in this review. Keywords: IntroductionBiotechnology based products are incredibly capturing market shares day by day. Chemistry based synthesis has a limitation when we talk about the tertiary and quaternary structure of large molecules such as protein. The human body is functioning by different biochemical reactions. Protein molecules are broadly involved in every aspect of the biological reaction. In the current paradigm, such functional proteins get expressed in microorganism by genetic variation as a part of the upstream process. Subsequently, these proteins are separated from the microorganisms and purified (as a downstream process) retaining its biological activity to inject in the human body. These complex proteins are difficult to cultivate, separate, characterize and reproduce [1,2].The basic mechanism of protein synthesis in any of the living organism involves transcription and translation of polynucleotide chain of Adenine, Guanine, Thymine, and Cytosine [3]. The sequence of the oligonucleotide is responsible for translating specific protein using a specific sequence of amino acid involved in the synthesis of protein. Currently marketed protein formulations readily provide biological action at the target site when injected into the body. Such protein molecules are produced outside of the human body and injected in purified and active form. However, the stability of proteins is the major concern in the development of protein formulations. Such biological molecules have a tertiary and qua...