title: Keratin-hydroxyapatite composites: biocompatibility, osseointegration, and physical properties in an ovine model.
abstract: Reconstituted keratin has shown promise as an orthopaedic biomaterial. This in vivo study investigates the biological response of composite materials prepared from reconstituted keratin containing a high content of hydroxyapatite (HA) (40 wt % HA), implanted for up to 18 weeks in the long bones of sheep. Keratin-HA composites were compared with a commercially available polylactic acid (PLA) HA composite (BIO RCI HA®, Smith and Nephew). Porous keratin-HA materials displayed excellent biocompatibility and osseointegration, with full integration into bone by 12 weeks. Dense keratin-HA materials also showed excellent biocompatibility, with a more limited osseointegration, involving the penetration of new bone into the periphery of the implant after eight weeks. In contrast, the PLA-HA implant did not integrate with surrounding tissue. Microindentation showed that porous keratin-HA implants were initially soft, but became stiffer as new bone penetrated the implant from four weeks onwards. In contrast, although the initial rigidity of dense keratin-HA composites was maintained for at least two weeks, the implant material weakened after four weeks. The PLA-HA implant maintained its physical properties throughout the course of the trial. This study demonstrates the increased osseointegration/osteoconduction capacity of keratin-HA composites and provides further evidence supporting the suitability of keratin-based materials, such as bone graft substitutes and soft tissue fixation devices.
authors.affiliation: Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand. george.dias@anatomy.otago.ac.nz
authors.forename: George J
authors.initials: GJ
authors.lastname: Dias
authors.forename: Patricia
authors.initials: P
authors.lastname: Mahoney
authors.forename: Michael
authors.initials: M
authors.lastname: Swain
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Kelly
authors.forename: Robert A
authors.initials: RA
authors.lastname: Smith
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Ali
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology*; D001696:Biomechanical Phenomena / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects / Q000473:pathology; D017886:Durapatite / Q000494:pharmacology*; D020007:Implants, Experimental; D007633:Keratins / Q000494:pharmacology*; D008422:Materials Testing / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D049329:Nanostructures / Q000737:chemistry; D016348:Osseointegration / Q000187:drug effects*; D016062:Porosity / Q000187:drug effects; D019919:Prosthesis Implantation; D034561:Sheep, Domestic / Q000502:physiology*; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D007633:Keratins; D017886:Durapatite