Modified siRNA

Due to the poor stability of siRNA, it is easily degraded by nucleases in vivo and is not easily absorbed by tissues, which limits its application in vivo. Chemical modification of the synthesized siRNA can increase the stability of siRNA and effectively inhibit the expression of the target gene. The correct modification can greatly promote the transformation of RNAi drugs from in vitro to in vivo and from laboratory to clinical application. The chemical modifications of siRNA mainly include three types: phosphate backbone modification, ribose modification and base modification. In addition, fluorescent dye labeling can also be used to track the absorption and distribution of siRNA in cells or animals.

Modification Choice

Type	Modification	5’	Intel	3’
Fluorescent groups	FAM	√		√
	Cy3	√		√
	Cy5	√		√
	HEX	√
	TET	√
	TAMRA	√		√
Quenched groups	BHQ-1			√
	BHQ-2			√
	MGB			√
	Dabcyl			√
Chemical groups	Biotin	√		√
	Biotin-teg	√		√
	C6-NH₂	√
	C7-NH₂			√
	Thiol	√		√
	Chol	√		√
	GalNAc			√
Special bases	LNA		√
	2’-O-Methyl		√
	2’-MOE		√
	2’-F		√
	5-Me-dC		√
	rl		√
	dl		√
Spacer	Spacer 9		√
	Spacer 18		√
	Spacer C3		√
	Spacer C6		√
Phosphorylation	PHOS	√		√
Thiophosphorylation	Phosphorothioate	√	√	√

* The modified RNA synthesis specification is within 5 OD, and the purification method is HPLC purification