title: In vivo bone formation by and inflammatory response to resorbable polymer-nanoclay constructs.
abstract: The development of synthetic bone grafts with requisite mechanical and morphological properties remains a key challenge in orthopaedics. Supercritical carbon dioxide (scCO2)-processed nanocomposites consisting of organically-modified montmorillonite clay dispersed in poly-d-lactide (PDLA) have shown structural and mechanical properties similar to corticocancellous bone. Using quantitative undecalcified histology and micro-computed tomography (μCT), time and material-dependent influences on in vivo bone formation, and inflammatory response were characterized. This represents the first in vivo evidence of the ability of scCO2-processed PDLA-nanoclay constructs to support osteogenesis, while eliciting an inflammatory response comparable to PDLA-hydroxyapatite materials. Histologic analyses demonstrated that the in vivo performance of nanoclay-containing PDLA constructs was similar to pure PDLA constructs, though nanocomposites demonstrated more radiodense bone at all time points (μCT analysis), and higher bone volume at 6 weeks. Taken with previous structural and mechanical studies, these in vivo analyses suggest that scCO2-processed, polymer-clay nanocomposites may be suitable structural bone graft materials.
  
  
  BACKGROUND
  With advances in science, orthopedic researchers have devoted significant amount of time in developing synthetic bone graft materials. Many of which are indeed currently in clinical use. In their previous studies, the authors described and studied supercritical carbon dioxide (scCO2)-processed nanocomposites consisting of organically modified montmorillonite clay dispersed in poly-D-lactide (PDLA) in in-vitro experiments. Here, in-vivo experiments were performed to investigate if this new material had improved mechanical properties, as well as the induction of inflammatory response. The overall positive findings may mean that this material could be used for future bone graft substitute applications.
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI USA.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Baker
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI USA.
authors.forename: Tristan
authors.initials: T
authors.lastname: Maerz
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI USA.
authors.forename: Hussein
authors.initials: H
authors.lastname: Saad
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Shaheen
authors.affiliation: Center for Nanomedicine Ophthalmology, Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, MD USA. Electronic address: Krangar1@jhmi.edu.
authors.forename: Rangaramanujam M
authors.initials: RM
authors.lastname: Kannan
mesh_terms: D000818:Animals; D001546:Bentonite / Q000009:adverse effects / Q000737:chemistry*; D018786:Bone Substitutes / Q000009:adverse effects / Q000737:chemistry*; D005260:Female; D007249:Inflammation / Q000209:etiology; D008807:Mice, Inbred BALB C; D053761:Nanocomposites / Q000009:adverse effects / Q000737:chemistry* / Q000648:ultrastructure; D010012:Osteogenesis; D011091:Polyesters / Q000009:adverse effects / Q000737:chemistry*; D055114:X-Ray Microtomography
chemical_list: D018786:Bone Substitutes; D011091:Polyesters; D001546:Bentonite; C033616:poly(lactide)
keywords: Bone graft; Bone scaffold; Nanoclay; Nanocomposites; Supercritical CO(2)