The Role Of Surface Chemistry In Osseointegration

Author : Emily Buck
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (126 download)

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Download or read book The Role of Surface Chemistry in Osseointegration written by Emily Buck and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Poly(etheretherketone) (PEEK) is a synthetic polymer with great potential for use as orthopedic implants with its radiolucency and mechanical properties close to those of native bone. Despite these advantages, PEEK implants tend to fail because immune cells, such as macrophages, prevent the attachment of bone by inducing chronic inflammation and fibrous encapsulation. Surface modification can improve osseointegration, but the mechanisms underlying the improvements are not well known. Since surface chemistry has been linked to reductions in fibrous encapsulation of model surfaces, this thesis aimed to investigate the effect of surface chemistry on the steps in the process of osseointegration, such as protein adsorption and macrophage responses, to provide insight about the role of surface chemistry in osseointegration. This thesis begins with a literature review that describes various surface modification strategies used to improve the integration of PEEK implants. The review proposed the development of surfaces with controlled properties to better understand how surface modifications influence the osseointegration of PEEK, and it highlighted a need for including protein adsorption and macrophage responses in future studies to better understand the full process of osseointegration around implants with modified surfaces. In the first study, a model surface, poly(styrene) (PS), with controlled surface chemistry was developed to investigate the effect of surface chemistry on protein adsorption and macrophage responses through diazonium chemistry reactions. Three common biological functional groups (COOH, NH2, and PO3H2) were selected and attached to PS surfaces in similar surface densities to compare the chemistries directly. Surfaces containing COOH groups increased the expression of anti-inflammatory macrophage markers while surfaces with NH2 groups exacerbated the response to an inflammatory stimulus. Characterization of the adsorbed protein layer demonstrated that surfaces with COOH groups adsorbed more proteins associated with integrin signaling from serum while surfaces with NH2 groups adsorbed more proteins associated with inflammatory reactions. These results demonstrated that surface chemistry could modulate macrophage responses through alterations in the layer of proteins adsorbed on the surfaces. In the second study, NH2 and COOH groups, which provoked pro- or anti-inflammatory macrophage responses, were selected and attached to PEEK surfaces to investigate whether these different macrophage responses could enhance the osseointegration of PEEK. In vitro, NH2 and COOH groups on PEEK promoted relatively pro- and anti-inflammatory macrophage responses as they did on PS, and protein adsorption on these surfaces also followed similar patterns. After 14 days in vivo, the NH2 groups promoted bone thinning while COOH groups had no effect. Surprisingly, the NH2 groups significantly increased adhesion to bone compared to the unmodified PEEK implants while COOH groups increased adhesion but not significantly. Since the NH2 groups were able to promote mineral deposition in acellular environments better than COOH groups, the NH2 groups may have enhanced mineral-binding in vivo. These results suggested different mechanisms involved in the osseointegration of NH2 and COOH-functionalized implants"--