Aptamers vs. antibodies.

		Aptamer	Antibody
Intrinsic qualities	Affinity	10 pM to10 μM	10 pM to10 μM
	Specificity	Highly specific	Highly specific
	Molecular weight	10–20 kDa	150 kDa (IgG)
	Synthesis method	Chemical	Biological
	Stability	pH 5 to 9, –80 to 100 °C, liquid or dry	pH 5 to 8, sequence specific, empirically determined, −80 to 4 °C
Application-related qualities	Selection speed	Days to weeks in vitro	Weeks in vivo
	Variability	Very uniform	Batch to batch
	Commercial cost of 1 mg	∼$50a	∼$2000–5000
	Chemical modifications	5′ end, 3′ end, internal; controlled	Primary amine, carboxylic acid, thiol chemistries; difficult to control

^aCost for DNA with no or simple chemical modifications (ex. thiol, amide, biotin)