CPP

Simple mixing method: Example: For MPG mediated gene delivery, peptide carrier/DNA complexes were formed in DMEM or phosphate-buffered saline (500 ml of DMEM containing 100 ng of DNA complexed with MPG at a charge ratio of 5:1) and incubated for 30 min at 37°C. Cells grown to 60% confluence were then overlaid with these preformed complexes.

CPPs pack oligonucleotides into nanocomplexes, which do not

dissociate in the presence of serum proteins and transfect cells more

efficiently than commercially available cationic lipids.

Many novel CPPs have been shown to transfect and trigger specific

biological response in a wide range of cell types, including challenging primary and suspension cells without being cytotoxic. In vivo experiments have revealed the capacity of CPP-mediated ONs to effectively inhibit tumor growth in tumor-bearing mice without triggering immune response, emphasizing even more the high therapeutic potential of CPP–ON

complexes.

Table: Application and effects of CPP-mediated siRNA

delivery by using noncovalent strategy

CPP	Cells/Model	Effect	Reference
MPG ac-GALFLGFLGAAGSTMGAWSQPKKKRKV-cys The cysteamide stabilises the carrier/DNA particle, as similarly reported for gene delivery mediated by cysteine-containing peptides.	HeLa and Cos-7 HS68, NIH-3T3	Cellular uptake of single- and double-stranded ONs 50 nmol/l siRNA→85% and 78% luciferase downregulation	Simeoni et al.
	HS68	100 nmol/l siRNA→60% GAPDH downregulation	Simeoni et al.
MPGΔNLS ac-GALFLGFLGAAGSTMGAWSQPKSKRKV-cys	HeLa and Cos-7	50 nmol/l siRNA→95% and 90% luciferase downregulation	Simeoni et al.
Stearyl-R8 st-RRRRRRRR-NH2 Polyarginine peptides, which are very efficient CPPs have been used for siRNA delivery into cells. Stearylated octaarginine (Stearyl-R8), are able to encapsulate and shuttle nucleic acids through cell membranes without the need to covalently attach the nucleic acid to the arginine-containing carrier peptide.	EGFP-expressing hippocampal neurons	16 nmol/l siRNA→>50% reduction in EGFP activity	Tönges et al.
EB1 LIKLWSHLIHIWFQNRRLKWKKK-amide	HeLa, HepG2	Luciferase downregulation	Lundberg et al.
Tat-DRBD GRKKRRQRRRPQ-DRBD	H1299, HUVEC, Jurkat T, hESC	>90% reduction in GAPDH mRNA level	Eguchi et al.
PF6 St-AGYLLGK[kk2sa4qn4]INLKALAALAKKIL-NH2	Hepatoma, MEF, HUVEC, mESC	Significant downregulation of HPRT1	El-Andaloussi et al.