Research ArticleBIOMATERIALS

Surface-Mediated Bone Tissue Morphogenesis from Tunable Nanolayered Implant Coatings

Science Translational Medicine  26 Jun 2013:
Vol. 5, Issue 191, pp. 191ra83
DOI: 10.1126/scitranslmed.3005576

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Implant Coating Builds Bone

With an aging population comes more and more surgical implants to stabilize broken hips and replace worn-down joints. Despite their widespread application, these biomedical implants can loosen by not integrating fully with the host tissue; this requires revision surgery and increases patient morbidity. In response, Shah and colleagues designed a series of biochemical coatings that can be applied to both polymer (PEEK) and metal (titanium) surfaces to help implants develop a strong interface with existing bone.

The so-called layer-by-layer assembly consisted of two parts: a base coating of several “osteoconductive” layers beneath degradable layers containing human BMP-2—a protein that promotes bone growth. These degradable layers were designed to control the release of BMP-2 over time, rather than delivering the protein all at once. In vivo in rat tibiae, Shah et al. found that the implants with the two-part coating were more difficult to pull out compared with single-coating or uncoated implants. This indicated better bonding between the coating materials and the host bone, and was confirmed on a cellular level by observing bone tissue on the surface of removed implants. In a rodent model, integration of implants with the multilayered coating was calculated to be stronger than the standard bioactive bone cement and other coatings tested in an animal model that are currently used in the clinic.

Through a successful proof-of-concept demonstration in rodents, Shah et al. show that this new layered approach could prevent implant loosening and associated morbidity in patients. Nevertheless, before moving into people, further testing will be needed in a larger animal model to confirm that the implants integrate with existing bone in a load-bearing environment.