title: Prolonged gene silencing in hepatoma cells and primary hepatocytes after small interfering RNA delivery with biodegradable poly(beta-amino esters).
abstract: BACKGROUND
  Small interfering (si)RNA mediated inhibition of oncogenes or viral genes may offer great opportunities for the treatment of several diseases such as hepatocellular carcinoma and viral hepatitis. However, the development of siRNAs as therapeutic agents strongly depends on the availability of safe and effective intracellular delivery systems. Poly(beta-amino esters) (PbAEs) are, in contrast to many other cationic polymers evaluated in siRNA delivery, biodegradable into smaller, nontoxic molecules.
  
  
  RESULTS
  We show for the first time that PbAE : siRNA complexes, containing 1,4-butanediol (PbAE1) or 1,6-hexanediol (PbAE2) diacrylate-based polymers, induced efficient gene silencing in both hepatoma cells and primary hepatocytes without causing significant cytotoxicity. Furthermore, carriers that slowly release the siRNA into the cytoplasm and hence induce a prolonged gene silencing are of major clinical interest, especially in fast dividing tumour cells. Therefore, we also studied the duration of gene silencing in the hepatoma cells and found that it was maintained for at least 5 days after siRNA delivery with PbAE2, the polymer with the slowest degradation kinetics.
  
  
  CONCLUSIONS
  From the time-dependent cellular distribution of these PbAE : siRNA complexes, we suggest that the slowly degrading PbAE2 causes a sustained endosomal release of siRNA during a much longer period than PbAE1. This may support the hypothesis that the endosomal release mechanism of PbAE : siRNA complexes is based on an increase of osmotic pressure in the endosomal vesicles after polymer hydrolysis. In conclusion, our results show that both PbAEs, and especially PbAE2, open up new perspectives for the development of efficient biodegradable siRNA carriers suitable for clinical applications.
authors.affiliation: Laboratory of General Biochemistry and Physical Pharmacy, Ghent University, Ghent, Belgium.
authors.forename: Roosmarijn E
authors.initials: RE
authors.lastname: Vandenbroucke
authors.forename: Bruno G
authors.initials: BG
authors.lastname: De Geest
authors.forename: Stefan
authors.initials: S
authors.lastname: Bonné
authors.forename: Mathieu
authors.initials: M
authors.lastname: Vinken
authors.forename: Tamara
authors.initials: T
authors.lastname: Van Haecke
authors.forename: Harry
authors.initials: H
authors.lastname: Heimberg
authors.forename: Ernst
authors.initials: E
authors.lastname: Wagner
authors.forename: Vera
authors.initials: V
authors.lastname: Rogiers
authors.forename: Stefaan C
authors.initials: SC
authors.lastname: De Smedt
authors.forename: Joseph
authors.initials: J
authors.lastname: Demeester
authors.forename: Niek N
authors.initials: NN
authors.lastname: Sanders
mesh_terms: D000256:Adenoviridae; D000818:Animals; D002072:Butylene Glycols; D006528:Carcinoma, Hepatocellular / Q000628:therapy*; D045744:Cell Line, Tumor; D004952:Esters / Q000737:chemistry; D020868:Gene Silencing; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D006018:Glycols; D022781:Hepatocytes; D006801:Humans; D018613:Microscopy, Confocal; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry; D034741:RNA, Small Interfering / Q000235:genetics*; D051381:Rats
chemical_list: D002072:Butylene Glycols; D004952:Esters; D006018:Glycols; D011108:Polymers; D034741:RNA, Small Interfering; C507253:poly(beta-amino ester); C039681:1,4-butanediol; C027765:hexamethylene glycol