Design and Development of Degradable Polyethylenimines for Delivery of DNA and Small Interfering RNA: An Updated Review

Table 2

Representative examples of degradable PEIs having disulfide linkage (modified from [103]).

Type	MW of starting PEI (Da)	Crosslinkers	Cells	Characters	Reference
Main chain	800	Dithiobis(succinimidyl-propionate, Dimethyl-3,3′-dithiobis propionimidate	CHO	The first synthesis of; the polymer	[19, 104]
	Ethylene amine monomers	Cystamine bisacrylamide	NIH3T3, bovine aortic endothelial, rat aortic smooth muscle	20-fold higher gene expression, Amido ethylenimine type	[29, 105]
	Ethylene diamine	Ethylene imine thiol	HeLa	Comparative transfection, Visualization of degradation of disulfide	[106]
	423	Cystamine bisacrylamide	Brain capillary endothelial	4.9-fold higher gene expression	[30]
	1500, 5000, 10800	Methoxy PEG thioacetate	CHO	Structure function relationship of PEG-PEI diblock copolymer	[59]
Side chain	2600, 3100, 4600	3,3′-Dithiopropionic acid di(𝑁-succinimidyl ester)	HEK	Importance in combination of branching density and cleavable bonds for siRNA delivery	[33, 97]
	800	Thiolated PEI	HeLa	Little serum dependency of transfection, Importance of disulfide content and MW of PEI on transfection	[32]
	1800	Cystamine	293T, HeLa	Click chemistry, Azide-terminated PEI	[107]
	1800	Polyaspartamide	293T	Click chemistry, azide-terminated polyaspartamide	[60]