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.

Hemostatic strategies for traumatic and surgical bleeding

“…Further investigation into keratin hydrogel hemostatic mechanisms revealed direct acceleration of the coagulation cascade, but a specific activation mechanism has not been specified leaving safety concerns . Keratin hydrogels are expected to be biocompatible and biodegradable through macrophage phagocytosis . However, neither has been reported for hemostatic application, and degradation timescales are not well characterized.…”

Novel keratin preparation supports growth and differentiation of odontoblast‐like cells

“…Keratin‐based scaffolds have been developed for bone tissue engineering (Dias et al . ,b, Kelly et al . ).…”

Osteoconduction in keratin-hydroxyapatite composite bone-graft substitutes

“…Only a few studies have investigated the in vivo properties of reconstituted keratin as an orthopaedic bone graft substitute . An initial in vivo study of the mass and physical strength of keratin bars in vivo (rat model) demonstrated the potential for keratin as a nonload‐bearing bone graft substitute .…”

“…Further in vivo investigations of keratin + 4% HA composites demonstrated the promising performance of porous materials, which showed excellent biocompatibility and osseointegration, with full integration into bone by 12 weeks. Microindentation showed that porous keratin–HA implants were initially soft but became stiffer as new bone penetrated the implant from 4 weeks onward …”