Table 3.

List of ligands for actively targeting the enteric epithelia.

Ligand	Target	Cell	Carrier	Biologic	Ref.
Folate	Folate receptor	Enterocyte	PLGA nanoparticles	Insulin	216
Biotin	Avidin	Enterocyte	Liposomes	Insulin	217
Vitamin B12	IF-CbI receptor∗	Enterocyte	Dextran nanoparticles; calcium phosphate nanoparticles	Insulin	218,219
Galactose	Galactose receptor	Macrophage	PLGA nanoparticles	siRNA	220
Mannose	Mannose receptor (DEC-205)	Enterocyte	Proliposome	Glutathione	221,222
Hyaluronate	CD44 receptor	Enterocyte	CaCO3 nanoparticles	Insulin	223
Transferrin	Transferrin receptor	Enterocyte	Fuse protein	Human growth hormone	224
Fc fragments	Neonatal Fc receptor	Enterocyte	PLA-PEG nanoparticles	Insulin	225
lectin	Integrin receptor	M-cell	Liposome; solid lipid nanoparticles	Insulin	168,226
RGD	Integrin αvβ3 receptor	Enterocyte; M-cell	PLGA-mPEG nanoparticles	Insulin	227
CSKSSDYQC (CSK)		Goblet cell	Chitosan nanoparticles	Insulin	228

IF-CBI: combination of gastric intrinsic factor (IF) and cobalamin (CbI, vitamin B12).