Barbieri Thesis - BioMedical Materials program (BMM)

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Chapter 6 – Flu uid uptake as insstructive factor Figure 14. Low magnificattion scans of (a) TCPS and (b) TTCPB explants stained s with meth hylene blue and basic ffuchsin. Arrows indicate bone (da ark red) whereass ceramics are dark d colored (i.e. brown and black). Sofft tissues are coolored with violet/blue and bonee marrow is whit te (stars). Due to t the long implantationn time (i.e. 6 moonths) it may be well that bone mmarrow is a cons sequence of occurring bone remodeling. Squares indiccate the spots where high maagnification imag ges were taken with light microscopyy (Figure 14). Figure 15. Microscopy detaails of (a) TCPS and a (b) TCPB expplants stained wit th methylene blue and basic fuchsin. Reed triangles showw residuals of deg graded ceramic. Black arrows ind dicate osteoblasts s and white arrows shoow osteocytes. SStars indicate on ngoing bone mattrix formation, le etters B and ST stands for mature bonne and soft tissuee respectively. 140
Chapter 6 – Fluid uptake as instructive factor As already mentioned in the introduction, the initial inflammatory response to the implantation of biomaterials may be one of the osteoinduction triggers. [218–220, 255, 256, 386] In fact, osteoclastogenesis and osteoblastogenesis at the biomaterial surface may be mediated by macrophage adhesion and subsequent secretion of cytokines. Unpublished preliminary in vitro results of members from our group showed that the culture of murine monocyte/macrophage cell line RAW 264.7 on osteoinductive ceramic resulted in significantly higher levels of secreted IL–6 and IL–4, cytokines responsible for osteoclastogenesis and foreign body giant cell fusion respectively, when compared to a non–inductive ceramic. Other data showed that osteoclastic markers in murine macrophage cell line J774.2 were significantly up–regulated during culture on osteoinductive ceramics, and stimulation of RAW 264.7 with osteoclast differentiation factor RANKL (receptor activator of NF–κB ligand) during culture on osteoinductive ceramics resulted in larger, more surface integrated osteoclast–like cells. Further evaluation of these macrophage/osteoclast culture systems may shed light on the potential osteogenic effects that such cell–material interactions may have on precursor cells. It should be observed that, in this study, the three composites had similar surface nano–structured topographies thus effects of surface topography on the composites in vivo performances can be excluded. Concluding, those composites (i.e. MLDL and MDL) that took up more fluids could quickly adsorb more biological molecules, which may have contributed to trigger certain inflammatory responses that may have increased the chance to trigger bone formation. On the contrary, things may have gone differently on MLD surfaces, which did not start any bone formation process. In vitro studies to unravel the role of early cellular response to osteoinductive composite are in progress. After six months we observed that MLDL showed significantly more bone compared to MDL. This may be explained by the fact that the composites have chemically different polymer phases. After five weeks accelerated degradation in phosphate buffered solution (PBS) we observed more fluid uptake in MDL than MLDL and MLD. Since the initial apatite chemistry and weight content was the same in the three materials, the different fluid absorption in the composites can be linked with the polymer physico–chemistry, i.e. the monomer and molecular weight. We observed that, after extrusion with apatite particles, differences in the viscosity molecular weights of the polymer phase in the three composites were minimal (±6 kDa). Based on this result, we assume that, in this study, the molecular weight did not play a crucial role. When the polymer is in contact with a liquid (e.g. water), its chains can move to reach an energetic equilibrium in the liquid–polymer contact eventually allowing more or less fluid penetration. [36,37] The monomer type influences on the polymer crystallinity. Particularly, polylactide having high D,L–lactide content is more amorphous. [387] Due to the little content of ordered regions (e.g. those 141
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INSTRUCTIVE COMPOSITES FOR BONE REG
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INSTRUCTIVE COMPOSITES FOR BONE REG
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献给潘臻 A mamma e papà A Stef
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Summary Summary Developing new biom
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Summary containing 96%mol. L-lactid
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Samenvatting De behoefte aan een de
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Samenvatting structuur, bespoedigt
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Riassunto velocità di dissoluzione
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Riassunto generale, ha migliorato i
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Chapter 1 - Introduction 1.1. Eukar
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Chap pter 1 - Introducction Interst
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Chapter 1 - Introduction bone marro
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Chap pter 1 - Introducction Figure
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Chapter 1 - Introduction regenerati
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Chapter 1 - Introduction Key concep
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Chapter 1 - Introduction grown in c
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Chapter 1 - Introduction Mainly, th
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Chapter 1 - Introduction All these
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Chap pter 1 - Introducction materia
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Chapter 1 - Introduction protein, m
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CHAPTER 2 The role of gels in bone
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Chapter 2 - The role of gels in ins
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CChapter 2 - The role r of gels in
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CHAPTER 3 Instructive composites: e
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Chapter 3 - Instructive composites:
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Chapter 3 - Instructive compos site
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CChapter 3 - Instructive composit t
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CHAPTER 4 Controlling dynamic mecha
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Chapter 4 - Conntrol of mechanical
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Chapter 4 - Control of mechanical a
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Chapter 8 - General discussion rese
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References [1] Waggoner B. Eukaryot
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References induction of rank in ost
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References [72] Kokovay E, Wang Y,
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References [102] McBeath R, Pirone
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References molecule-mediated TGF- t
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References [159] Autumn K, Sitti M,
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References [189] Teixeira AI, McKie
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References [215] Tang L, Jennings T
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References [242] Wei G, Ma PX. Stru
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References [270] Atkinson BL, Hanks
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References [297] Sato I, Akizuki T,
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References hematopoietic stem cell
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References [352] Cullinane DM, Sali
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References [382] Norde W, Giacomell
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References differentiation of rat B
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Acknowledgments thank you for all t
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Acknowledgments desidero tutto il m
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Barbieri Thesis - BioMedical Materials program (BMM)

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