title: Design of pH-sensitive peptides from natural antimicrobial peptides for enhancing polyethylenimine-mediated gene transfection.
abstract: BACKGROUND
  Poor endosomal release is a major barrier of polyplex-mediated gene transfection. Antimicrobial peptides (AMPs) are commonly used to improve polyethylenimine (PEI)-mediated gene transfection by increasing endosomal release. In the present study, we designed novel pH-sensitive peptides that highly enhance transfection efficiency compared to their parent peptides.
  
  
  METHODS
  Two analogues of melittin (Mel) and RV-23 (RV) were synthesized by replacing the positively-charged residues in their sequences with glutamic acid residues. The pH-sensitive lysis ability of the peptides, the effect of the peptides on physicochemical characteristics, the intracellular trafficking, the transfection efficiency, and the cytotoxicity of the polyplexes were determined.
  
  
  RESULTS
  The acidic peptides showed pH-sensitive lytic activity. The hemolytic activity of acidic peptides at pH 5.0 was higher than that at pH 7.4. The incorporation of acidic peptides did not affect the DNA binding ability of PEI but affected the physicochemical characteristics of the PEI/DNA polyplexes, which may be beneficial for endosomal release and gene transfection. The incorporation of acidic peptides into PEI/DNA polyplexes enhanced the PEI-mediated transfection efficiency corresponding to up to 42-fold higher luciferase activity compared to that of PEI alone.
  
  
  CONCLUSIONS
  The results of the present study indicate that replacement of positively-charged residues with glutamic acid residues in the AMP sequence yields pH-sensitive peptides, which enhance the transfection efficiency of PEI/DNA polyplexes in various cell lines.
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Shi-Kun
authors.initials: SK
authors.lastname: Zhang
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Jin-Wen
authors.initials: JW
authors.lastname: Song
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Su-Bo
authors.initials: SB
authors.lastname: Li
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Gao
authors.affiliation: Department of Paediatrics, General Hospital of the PLA Rocket Force, Beijing, China.
authors.forename: Hong-Yu
authors.initials: HY
authors.lastname: Chang
authors.affiliation: Neonatal Department of Xi'an No 4 Hospital, Xi'an, China.
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Jia
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Gong
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Ying-Xia
authors.initials: YX
authors.lastname: Tan
authors.affiliation: Department of Tissue Engineering, Beijing Institute of Transfusion Medicine, Beijing, China.
authors.forename: Shou-Ping
authors.initials: SP
authors.lastname: Ji
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D004247:DNA / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D018014:Gene Transfer Techniques; D006367:HeLa Cells; D056945:Hep G2 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008555:Melitten / Q000737:chemistry; D010455:Peptides / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D011094:Polyethyleneimine / Q000737:chemistry*; D014162:Transfection / Q000379:methods
chemical_list: D000890:Anti-Infective Agents; D010455:Peptides; D008555:Melitten; D011094:Polyethyleneimine; D004247:DNA
keywords: Glu replacement; antimicrobial peptides; endosomal release; gene transfection; pH-sensitive peptides; polyethylenimine (PEI)