title: Silk as a biocohesive sacrificial binder in the fabrication of hydroxyapatite load bearing scaffolds.
abstract: Limitations of current clinical methods for bone repair continue to fuel the demand for a high strength, bioactive bone replacement material. Recent attempts to produce porous scaffolds for bone regeneration have been limited by the intrinsic weakness associated with high porosity materials. In this study, ceramic scaffold fabrication techniques for potential use in load-bearing bone repairs have been developed using naturally derived silk from Bombyx mori. Silk was first employed for ceramic grain consolidation during green body formation, and later as a sacrificial polymer to impart porosity during sintering. These techniques allowed preparation of hydroxyapatite (HA) scaffolds that exhibited a wide range of mechanical and porosity profiles, with some displaying unusually high compressive strength up to 152.4 ± 9.1 MPa. Results showed that the scaffolds exhibited a wide range of compressive strengths and moduli (8.7 ± 2.7 MPa to 152.4 ± 9.1 MPa and 0.3 ± 0.1 GPa to 8.6 ± 0.3 GPa) with total porosities of up to 62.9 ± 2.7% depending on the parameters used for fabrication. Moreover, HA-silk scaffolds could be molded into large, complex shapes, and further machined post-sinter to generate specific three-dimensional geometries. Scaffolds supported bone marrow-derived mesenchymal stem cell attachment and proliferation, with no signs of cytotoxicity. Therefore, silk-fabricated HA scaffolds show promise for load bearing bone repair and regeneration needs.
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA, USA.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: McNamara
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA, USA; Graduate School of Biomedical Engineering, UNSW Australia, Sydney, NSW, Australia.
authors.forename: Jelena
authors.initials: J
authors.lastname: Rnjak-Kovacina
authors.affiliation: Department of Plastics Engineering, University of Massachusetts Lowell, Lowell, MA, USA.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Schmidt
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA, USA.
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Lo
authors.affiliation: Department of Biomedical Engineering, Tufts University, Medford, MA, USA. Electronic address: David.Kaplan@Tufts.edu.
authors.forename: David L
authors.initials: DL
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D012831:Bombyx; D001854:Bone Marrow Cells; D018786:Bone Substitutes; D002448:Cell Adhesion / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival; D002516:Ceramics / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D008297:Male; D008422:Materials Testing; D059630:Mesenchymal Stem Cells / Q000187:drug effects; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D047011:Silk / Q000737:chemistry*; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry*; D016474:Weight-Bearing; D014961:X-Ray Diffraction
chemical_list: D018786:Bone Substitutes; D047011:Silk; D017886:Durapatite
keywords: Bone tissue engineering; Ceramic structure; Hydroxyapatite; Porosity; Silk