Fig. 1
From: Advances in aptamer screening and aptasensors’ detection of heavy metal ions
A schematic diagram of SELEX. The initial library contains about 1014–1016 random oligonucleotides, which is composed of fixed primer sequences with 18–25 bp at both ends and 30–60 bp in the middle. The aptamer is obtained after several rounds of selection, including binding, separation, amplification and purification, and the products are used in the next round of selection