Aptamers are short DNA or RNA oligonucleotides with high, specific affinity to a special target. The name was originated from aptus that means "to fit" and meros that shows the polymer identity of oligonucleotides (1, 2). Aptamer characteristics provide prominent potential applications in multiple fields.These nucleic acid ligands are completely generated through in vitro process for a wide range of targets from small molecules and ions to large proteins and cells and even whole organism or tissue. Their chemical modifications could be easily performed to improve the intended specificity. Meanwhile, they keep their stability against various conditional stresses and show lower toxicity and immunogenicity than other specific ligands e.g. monoclonal antibodies. Because of the high specificity, adaptability, and ease of modification, aptamers have been used in a broad range of applications, including affinity purification, drug discovery, high-throughput screening, drug delivery, medical diagnostics and biosensors (3-5).
In molecular biology, there are several methods that could help researchers for in vitro evolution of single stranded oligonucleotide pools to high affinity ligands like aptamers. In vitro evolution is the experimental process in which large random-sequence pools of RNA or DNA are used as the starting point and particular nucleic acid sequences with higher affinity to an intended target are identified as aptamers. This type of selection and evolution is termed