Table 1.

Comparison between aptamers and antibodies. A comparison of critical features of aptamers shows how aptamers can supplement monoclonal antibodies.

	Aptamers	Antibodies
Stability	Withstand repeated rounds of denaturation/renaturation. Temperature resistant: stable at room temperature. Long shelf life (several years). Can be lyophilized. Degradable by nucleases. Resistant to proteases.	Easily denatured. Temperature sensitive and require refrigeration to avoid denaturation. Limited shelf life. Must be refrigerated for storage and transport. Degradable by proteases. Resistant to nucleases.
Synthesis	In vitro SELEX takes only 2–8 weeks. No batch-to-batch variation. Cheap to synthesize.	Produced in vivo. More than 6 months. Batch-to-batch variations. Laborious and expensive.
Target potential	From ions and small molecules to whole cells and live animals.	Targets must cause a strong immune response for antibodies to be produced.
Size	Small molecules.	Relatively large by comparison.
Modifiability	Aptamers can readily and easily be modified without affinity loss.	Modifications often lead to reduced activity.
Affinity	High and increased in multivalent aptamers.	Dependent on the number of epitopes on the antigen.
Specificity	Single point mutations identifiable.	Different antibodies might bind the same antigen.
Tissue uptake/kidney filtration	Fast.	Slow.