title: Development of adenovirus immobilization strategies for in situ gene therapy.
abstract: BACKGROUND
  Regenerative gene therapy using viral vectors enables transduced cells to express bioactive factors in vivo. Viral delivery with spatial control can enhance transduction efficiency and may limit systemic infection. Consequently, we tethered biotinylated adenovirus via interactions with avidin on chitosan surfaces to gain robust control for in situ transduction.
  
  
  METHODS
  Avidin was either directly conjugated to chitosan (virus-biotin-avidin-material; VBAM) or indirectly docked on biotinylated chitosan surfaces (virus-biotin-avidin-biotin-material; VBABM) to tether biotinylated adenovirus. Enzyme-linked immunosorbent assay (ELISA) and spectroscopic analysis were performed to demonstrate the binding profiles. Biotin-alkaline phosphatase and biotinylated adenovirus were used as different sized particles to evaluate binding efficiencies and were compared by the Sips isotherm adsorption method. Scanning electron microscopy (SEM) examination illustrated virus distribution, and the transduction efficiency was determined by in vitro cell transduction.
  
  
  RESULTS
  ELISA and spectroscopic analysis both demonstrated that the VBAM system led to multilayer avidin formation on biomaterial surfaces, whereas VBABM formed a monolayer of avidin. Sips isotherm adsorption indicated that the VBAM method increased heterogeneity and steric hindrance of binding sites. By contrast, the VBABM method docked avidin on chitosan surfaces and orientated the binding sites to facilitate ligand binding. In addition, SEM images illustrated that the VBABM method led to more even viral distribution. In vitro cell infection experiments also demonstrated that the VBABM system enhanced virus immobilization and thus improved cell transduction efficiency over the VBAM system.
  
  
  CONCLUSIONS
  The VBABM strategy is a superior method for in situ transduction from biomaterials. This strategy could be adapted for use with a variety of biomaterials as well as viral vectors, and thus may be an alternative method for in vivo regenerative gene therapy.
authors.affiliation: -epartment of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109-1078, USA.
authors.forename: Wei-Wen
authors.initials: WW
authors.lastname: Hu
authors.forename: Michael W
authors.initials: MW
authors.lastname: Lang
authors.forename: Paul H
authors.initials: PH
authors.lastname: Krebsbach
mesh_terms: D000256:Adenoviridae / Q000235:genetics* / Q000378:metabolism; D001360:Avidin / Q000737:chemistry / Q000378:metabolism; D001710:Biotin / Q000737:chemistry / Q000378:metabolism; D019921:Biotinylation; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D008855:Microscopy, Electron, Scanning; D014161:Transduction, Genetic / Q000379:methods*
chemical_list: D001360:Avidin; D001710:Biotin