No abstract

Biomimicking ceramics have been developed to induce efficient recovery of damaged hard tissues. Among them, calcium phosphate-based bioceramics have been the most widely used because of their similar composition with human hard tissue and excellent biocompatibilities. However, the incomplete understanding of entire inorganic phases in natural bone has limited the recreation of complete bone compositions. In this work, broad biomedical evaluation of whitlockite (WH: Ca18Mg2(HPO4)2(PO4)12), which is the secondary inorganic phase in bone, is conducted to better understand human hard tissue and to seek potential application as a biomaterial. Based on the recently developed gram-scale method for synthesizing WH nanoparticles, the properties of WH as a material for cellular scaffolding and bone implants are assessed and compared to those of hydroxyapatite (HAP: Ca10(PO4)6(OH)2) and β-tricalcium phosphate (β-TCP: β-Ca3(PO4)2). WH-reinforced composite scaffolds facilitate bone-specific differentiation compared to HAP-reinforced composite scaffolds. Additionally, WH implants induce similar or better bone regeneration in calvarial defects in a rat model compared to HAP and β-TCP implants, with intermediate resorbability. New findings of the properties of WH that distinguish it from HAP and β-TCP are significant in understanding human hard tissue, mimicking bone tissue at the nanoscale and designing functional bioceramics.

PEEK is a bioinert material that does not chemically bind to native bone tissue and thus formation of natural bone-like hydroxyapatite (HA) coating layer on PEEK has been an important challenge to improve biocompatibility and to preserve mechanical property of PEEK. Among various coating techniques, cold-spray coating method is suitable to form stable HA coating layer on PEEK while maintaining their chemical properties, because it can be conducted in relatively low-temperature range. Therefore, in this research, we used cold-spray coating method to form a thick layer of HA on the topographically complex PEEK substrates with periodic ridges on the surface and implanted in iliac bone defects of minipigs which is known to be similar with human body system. In addition, PEEK cage for clinical usage was coated with HA and inserted in the lumbar intervertebral disc space of minipig. We observed higher ALP activity, calcium production, and BSP production of human bone marrow mesenchymal stem cells on the HA-coated PEEK implants than the bare PEEK group in in vitro test. In addition, two-dimensional histological analysis and three-dimensional micro CT analysis demonstrated that implantation of complex shape of HA-PEEK hybrid implant in in vivo minipig model resulted sufficient biocompatibility and osseointegration for further clinical applications. Notably, due to the enhanced stability of PEEK cage induced from HA coating layer, osseointegration rate of the small HA blocks loaded inside the PEEK cage was also significantly improved which indicates overall increased fusion rate and adherence of the HA-coated PEEK cage. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 647-657, 2017.