title: A pH-sensitive multifunctional gene carrier assembled via layer-by-layer technique for efficient gene delivery.
abstract: BACKGROUND
  The success of gene therapy asks for the development of multifunctional vectors that could overcome various gene delivery barriers, such as the cell membrane, endosomal membrane, and nuclear membrane. Layer-by-layer technique is an efficient method with easy operation which can be used for the assembly of multifunctional gene carriers. This work describes a pH-sensitive multifunctional gene vector that offered long circulation property but avoided the inhibition of tumor cellular uptake of gene carriers associated with the use of polyethylene glycol.
  
  
  METHODS
  Deoxyribonucleic acid (DNA) was firstly condensed with protamine into a cationic core which was used as assembly template. Then, additional layers of anionic DNA, cationic liposomes, and o-carboxymethyl-chitosan (CMCS) were alternately adsorbed onto the template via layer-by-layer technique and finally the multifunctional vector called CMCS-cationic liposome-coated DNA/protamine/DNA complexes (CLDPD) was constructed. For in vitro test, the cytotoxicity and transfection investigation was carried out on HepG2 cell line. For in vivo evaluation, CMCS-CLDPD was intratumorally injected into tumor-bearing mice and the tumor cells were isolated for fluorescence determination of transfection efficiency.
  
  
  RESULTS
  CMCS-CLDPD had ellipsoidal shapes and showed "core-shell" structure which showed stabilization property in serum and effective protection of DNA from nuclease degradation. In vitro and in vivo transfection results demonstrated that CMCS-CLDPD had pH-sensitivity and the outermost layer of CMCS fell off in the tumor tissue, which could not only protect CMCS- CLDPD from serum interaction but also enhance gene transfection efficiency.
  
  
  CONCLUSIONS
  These results demonstrated that multifunctional CMCS-CLDPD had pH- sensitivity, which may provide a new approach for the antitumor gene delivery.
authors.affiliation: School of Pharmaceutical Science, Shandong University, Jinan, Shandong, People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.forename: Donghua
authors.initials: D
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Miao
authors.forename: Chunxi
authors.initials: C
authors.lastname: Liu
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Sun
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Liu
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry; D048271:Chitosan / Q000031:analogs & derivatives / Q000737:chemistry / Q000493:pharmacokinetics; D004247:DNA / Q000737:chemistry* / Q000493:pharmacokinetics; D004355:Drug Stability; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D056945:Hep G2 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000097:blood / Q000737:chemistry* / Q000493:pharmacokinetics; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D010316:Particle Size; D011479:Protamines / Q000737:chemistry / Q000493:pharmacokinetics; D014162:Transfection / Q000379:methods*
chemical_list: D002412:Cations; D008081:Liposomes; D011479:Protamines; C514968:carboxymethyl-chitosan; D049452:Green Fluorescent Proteins; D004247:DNA; D048271:Chitosan