An aptamer is an nucleic acid that binds a target molecule.
Comparison to Antibodies
Like antibodies, RNA aptamers can be extremely specific to a target and are capable of discriminating between closely related molecules. RNA aptamers and antibodies can be generated to bind a similarly diverse array of targets. Antibodies, however, are composed of protein and must be produced by the immune cells of a living organism. Novel aptamers can be selected quicky in vitro and amplified by PCR.
Selection of Aptamers
RNA aptamers are generated by selection. The selection process begins with a large library of random sequences and removes RNAs that do not bind the target or bind nonspecifically. The selected RNAs are isolated, reverse-transcribed, amplified, and the process is repeated.