title: Biocompatibility and Bone Formation of Flexible, Cotton Wool-like PLGA/Calcium Phosphate Nanocomposites in Sheep.
abstract: BACKGROUND
  The purpose of this preliminary study was to assess the in vivo performance of synthetic, cotton wool-like nanocomposites consisting of a biodegradable poly(lactide-co-glycolide) fibrous matrix and containing either calcium phosphate nanoparticles (PLGA/CaP 60:40) or silver doped CaP nanoparticles (PLGA/Ag-CaP 60:40). Besides its extraordinary in vitro bioactivity the latter biomaterial (0.4 wt% total silver concentration) provides additional antimicrobial properties for treating bone defects exposed to microorganisms.
  
  
  METHODS
  Both flexible artificial bone substitutes were implanted into totally 16 epiphyseal and metaphyseal drill hole defects of long bone in sheep and followed for 8 weeks. Histological and histomorphological analyses were conducted to evaluate the biocompatibility and bone formation applying a score system. The influence of silver on the in vivo performance was further investigated.
  
  
  RESULTS
  Semi-quantitative evaluation of histology sections showed for both implant materials an excellent biocompatibility and bone healing with no resorption in the adjacent bone. No signs of inflammation were detectable, either macroscopically or microscopically, as was evident in 5 µm plastic sections by the minimal amount of inflammatory cells. The fibrous biomaterials enabled bone formation directly in the centre of the former defect. The area fraction of new bone formation as determined histomorphometrically after 8 weeks implantation was very similar with 20.5 ± 11.2 % and 22.5 ± 9.2 % for PLGA/CaP and PLGA/Ag-CaP, respectively.
  
  
  CONCLUSIONS
  The cotton wool-like bone substitute material is easily applicable, biocompatible and might be beneficial in minimal invasive surgery for treating bone defects.
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zurich, Switzerland.
authors.forename: Oliver D
authors.initials: OD
authors.lastname: Schneider
authors.forename: Dirk
authors.initials: D
authors.lastname: Mohn
authors.forename: Roland
authors.initials: R
authors.lastname: Fuhrer
authors.forename: Karina
authors.initials: K
authors.lastname: Klein
authors.forename: Käthi
authors.initials: K
authors.lastname: Kämpf
authors.forename: Katja M R
authors.initials: KM
authors.lastname: Nuss
authors.forename: Michèle
authors.initials: M
authors.lastname: Sidler
authors.forename: Katalin
authors.initials: K
authors.lastname: Zlinszky
authors.forename: Brigitte
authors.initials: B
authors.lastname: von Rechenberg
authors.forename: Wendelin J
authors.initials: WJ
authors.lastname: Stark