Table 2.

The Effect of Various Surface Modification Materials of Nanoparticles on the Oral Administration

Material	Influential Effect	Ref
PEG	Increasing mucus penetration (~5 KDa)	[62]
	Reduce recognition and clearance	[37,71]
	Enhance plasma circulation times	[71]
	Promote drug accumulation	[37]
TA	Improve solubility of hydrophobic molecules	[75]
	Inhibitory effect of P-gp	[81]
	Avoid gastric acid degradation	[2]
Polycation	Increase solubility of hydrophobic molecules	[84]
PECs	Facilitating mucus transport	[43,85]
	Increasing cellular penetration	[89]
Lipid material (log P>5)	Increase the lymphatic absorption Prevent the liver from first pass metabolizing	[84]
		[84]
Specific ligands	Increasing cellular uptake	[96]

Abbreviations: PEG, ploy(ethylene glycol); TA, tannic acid; PECs; polyelectrolyte complexes; P-gp, P-glycoprotein.