The Role of Surface Chemistry in the Osseointegration of PEEK Implants

Poly(etheretherketone) (PEEK) implants suffer from poor osseointegration because of chronic inflammation. In this study,we hypothesized that adding NH2and COOH groups to the surface of PEEK could modulate macrophage responses by altering proteinadsorption and improve its osseointegration. NH2and COOH-functionalized PEEK surfaces induced pro- and anti-inflammatorymacrophage responses, respectively, and differences in proteinadsorption patterns on these surfaces were related to the variedinflammatory responses. The macrophage responses to NH2surfacessignificantly reduced the osteogenic differentiation of mesenchymal stem cells (MSCs). MSCs cultured on NH2surfacesdifferentiated less than those on COOH surfaces even though NH2surfaces promoted the most mineralization in simulated bodyfluid solutions. After 14 days in rat tibia unicortical defects, the bone around NH2surfaces had thinner trabeculae and higher specificbone surface than the bone around unmodified implants; surprisingly, the NH2implants significantly increased bone-binding over the unmodified implants, while COOH implants only showed a trend for increasing bone-binding. Taken together, these results suggest that both mineral-binding and immune responses play a role in osseointegration, and PEEK implant integration may be improved with mixtures of these two functional groups to harness the ability to reduce inflammation and bind bone strongly

Automated summary

Poly(etheretherketone) (PEEK) implants with added NH2 and COOH groups on their surface can modulate macrophage responses and improve osseointegration. NH2-functionalized surfaces induce pro-inflammatory macrophage responses, while COOH-functionalized surfaces induce anti-inflammatory macrophage responses. The protein adsorption patterns on these surfaces are related to the varied inflammatory responses. NH2 surfaces inhibit the osteogenic differentiation of mesenchymal stem cells (MSCs) compared to COOH surfaces, despite promoting more mineralization in simulated body fluid solutions. In the rat tibia unicortical defects study, the bone around NH2 surfaces had thinner trabeculae and higher specific bone surface, indicating improved bone binding compared to unmodified implants. COOH surfaces only showed a trend in increasing bone binding. The results suggest that a combination of both mineral-binding and immune responses can improve osseointegration of PEEK implants.