Table 1.

Advantages and limitations of common targeting agents used in nanotherapeutics

Targeting agent	Antibodies	Aptamers	Peptides	Small molecules
Advantages	● Easily conjugated	● Low cost	● Systematic development	● Low cost
	● Therapeutic effect	● Low immunogenicity	● Small size	● Easily conjugated
		● High affinity	● Low cost	● High stability
		● Small size	● Some can mediate endosomal escape
		● Easily chemically modified
Limitations	● Affinity varies with conjugation approach	● Rapidly degraded if unmodified	● Biodistribution varies	● Non-systematic approaches for development
	● High cost	● Cross-reactivity	● Toxicology varies	● Lack high specificity
	● Limited tumor penetration	● Binding affinity susceptible to environment
	● High immunogenicity
	● Large size