Table 1.

Properties of aptamers versus antibodies

Aptamers	Antibodies
Binding affinity in low nanomolar to picomolar range	Binding affinity in low nanomolar to picomolar range
Entire selection is a chemical process carried out in vitro and can therefore target any protein	Selection requires a biological system, therefore difficult to raise antibodies to toxins (not tolerated by animal) or nonimmunogenic targets
Can select for ligands under a variety of conditions for in vitro diagnostics	Limited to physiological conditions for optimizing antibodies for diagnostics
Iterative rounds against known target limit screening processes	Screening monoclonal antibodies is time-consuming and expensive
Uniform activity regardless of batch synthesis	Activity of antibodies varies from batch to batch
Pharmacokinetic parameters can be changed on demand	Difficult to modify pharmacokinetic parameters
Investigator determines target site of protein	Immune system determines target site of protein
Wide variety of chemical modifications to molecule for diverse functions	Limited modifications to molecule
Return to original conformation after temperature insult	Temperature sensitive and undergo irreversible denaturation
Unlimited shelflife	Limited shelf life
No evidence of immunogenicity	Significant immunogenicity
Cross-reactive compounds can be isolated using toggle strategy to facilitate preclinical studies	No method for isolating cross-reactive compound
Aptamer-specific antidote can be developed to reverse the inhibitory activity of the drug	No rational method to reverse molecules