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In SELEX method, an RNA or DNA library of oligonucleotides is chemically synthesized and each RNA and DNA strands in libraries will contain 40-100 base pair which randomly builds a flanked region. Ordinary, 5′ and 3′ PCR primer binding sequences create a flanked region in the DNA or RNA library.
Generally, DNA aptamers contain 1014-1015 sequences so they fold into a special structure, and then incubate with their target ligands. Aptamers bind to special targets with high affinity which are amplified by polymerase chain reaction (PCR) technique (Fig.1) (20). This ability of aptamers is used to identify different molecules in an in vivo and in vitro
