title: Controlled gene delivery system based on thermosensitive biodegradable hydrogel.
abstract: OBJECTIVE
  Currently, most pDNA delivery systems based on synthetic polymers are either nonbiodegradable or not sensitive to the release environment. The primary objective of this study was to develop and evaluate an aqueous-based, thermosensitive, biodegradable and biocompatible triblock copolymer to control pDNA delivery in vitro and in vivo.
  
  
  METHODS
  The triblock copolymers, poly[ethylene glycol-b-(D, L-lactic acid-co-glycol acid)-b-ethylene glycol] (PEG-PLGA-PEG), were synthesized as previously described. The molecular weight and polydispersity of PEG-PLGA-PEG were monitored by gel permeation chromatography (GPC). The cytotoxicity of PEG-PLGA-PEG was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The release of 32P-labeled pDNA entrapped in aqueous dispersion of PEG-PLGA-PEG in 0.1 mol/L sodium phosphate buffer solution (pH 7.4) was studied at 37 degrees C under agitation. Gene transfection efficiency was evaluated in a skin wound model in CD-1 mice.
  
  
  RESULTS
  The aqueous dispersion of PEG-PLGA-PEG flows freely at room temperature but form a gel at 37 degrees C body temperature. The in vitro degradation of PEG-PLGA-PEG lasted for more than 30 days. The cytotoxicity of PEG-PLGA-PEG evaluated in HEK 293 cells was significantly lower than that of poly-L-lysine hydrochloride. The release profile of supercoiled pDNA from the polymer followed the zero-order kinetics up to 12 days. Maximal gene expression of luciferase was at 24 h in the skin wound of CD-1 mice and by 72 h, the expression dropped by nearly 94%.
  
  
  CONCLUSIONS
  These results suggest hydrogel formed by PEG-PLGA-PEG could be a promising platform for delivery of pDNA, which represents a novel strategy that may serve as a non-viral vector for gene therapy in wound healing.
authors.affiliation: Center for Pharmacogenetics, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Zhenhua
authors.initials: Z
authors.lastname: Li
authors.forename: Wen
authors.initials: W
authors.lastname: Ning
authors.forename: Jumei
authors.initials: J
authors.lastname: Wang
authors.forename: Augustine
authors.initials: A
authors.lastname: Choi
authors.forename: Pui-Yan
authors.initials: PY
authors.lastname: Lee
authors.forename: Pradeep
authors.initials: P
authors.lastname: Tyagi
authors.forename: Leaf
authors.initials: L
authors.lastname: Huang
mesh_terms: D000818:Animals; D001711:Biotransformation; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000008:administration & dosage*; D004339:Drug Compounding; D018014:Gene Transfer Techniques; D020100:Hydrogels / Q000737:chemistry / Q000633:toxicity; D007773:Lactates; D008156:Luciferases / Q000737:chemistry / Q000235:genetics; D051379:Mice; D011092:Polyethylene Glycols; D013816:Thermodynamics; D014945:Wound Healing / Q000235:genetics
chemical_list: D020100:Hydrogels; D007773:Lactates; C088513:poly(lactic acid-ethylene glycol); D011092:Polyethylene Glycols; D004247:DNA; D008156:Luciferases