Abstract: Systematic Evolution of Ligand by Exponential enrichment (SELEX) is a new combinational chemistry methodology for in vitro selection of specific aptamers. Aptamers are artificial oligonucleotide ligands that are capable of high-affinity binding to target molecules, such as amino acids, drugs, proteins and other small molecules or ions etc. They are isolated from combinational libraries of synthetic oligonucleotide by an iterative process of affinity selection, recovery and amplification. Several properties of aptamers make them an attractive class of therapeutic compounds. Their affinity and specificity for a given protein make it possible to isolate a ligand to nearly any target, and adjusting their bioavailability expands their clinical utility. Aptamers may prove useful in the treatment of a wide variety of human diseases, including infectious illness, cancer, and cardiovascular diseases. We review the development of this emerging class of therapeutics, summarize progress to date, and speculate on the eventual utility of such agents in the clinic.

Key words: SELEX, aptamer, ligand, oligonucleotide, library