Barbieri Thesis - BioMedical Materials program (BMM)

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CChapter 3 – Instructive composit tes: effect of filller content on osteoinduction Figure 3. BSSEM pictures shoowing the apatite e particles distribuution in the polylactide matrix for (a) 0% CaP, i.e. poly(D,L– –lactide), (b) 10% % CaP, (c) 20% CaP and (d) 400% CaP specime ens. Polymer ma atrix is black, while apatite particles are white. Table 4. Ubbbelohde measureements of inhere ent (inh) and inttrinsic () viscosity, and calcu ulated weight average moleecular weight (MMw) for the polym mer as supplied and after proces ssing in acetone e with apatite particles. Staatistical comparisoon is done on Mw w and is expresseed in terms of p–v value. As supplied 0% CaP 10% CaP 220% CaP 40 0% CaP 0.47±0.01 0.44±0.02 0.46±0.01 00.47±0.01 0. 45±0.03 0.48±0.02 0.44±0.01 0.46±0.03 00.48±0.02 0. 46±0.01 56.3±1.7 51.7±1.3 54.7±1.1 556.9±0.9 53 3.5±1.1 >0.07 for all ccomparison comb bination except wwhen comparing the t polymer as supplied with 0%CaP where p
Chapter 3 – Instructive composites: effect of filler content on osteoinduction apatite contents no mineralization was seen within 14 days (Figures 6). The mineralization increased with time on the 40% CaP surface, as indicated by both the extension and the thickness of the covering calcified layer (Figures 6). 3.3.6. Ectopic bone formation A total of seven samples per material were intramuscularly implanted in seven dogs. After 12 weeks, all samples were retrieved and they were surrounded by a thin layer of connective tissue and then muscle tissue. As shown in the histological overview (Figure 6), only the 40% CaP specimens retained their shape after 12 weeks of implantation (Figure 7), while all samples with lower CaP content collapsed (Figures 7a, 7b, 6c). It was also observed that only 40% CaP implants had de novo bone tissue in their pores (n=7) (Figure 7). Closer observation (Figure 8) showed that both non–mineralized and mineralized bone had formed tight to the pore surface of all 40% CaP implants. Active osteoblast–like cells were present on the outer surface of the newly formed bone (Figure 8), indicating that there was still active bone formation after 12 weeks of implantation. At the same time, osteocytes were observed within lacunae in the mineralized bone (Figure 8). Histomorphometry analysis quantified the area percentage of bone in the available space of 40% CaP as 4.9±4.5% (Table 5). Fluorescent microscopy showed that all 40% CaP specimens contained three colours: green, red and yellow (Figure 9). The colour green (calcein injected at week 3) was seen within the composite material and may indicate in vivo mineralization of the implants, and not bone formation. However, the presence of calcein in the material may also mean adsorption of the fluorochrome on the composite at free binding sites formed after probable degradation of the composite. Red (xylenol orange injected at week 6) and yellow (tetracycline injected at week 9) fluorescent labels were seen within bone tissue deposited on the material surface and indicate that bone formation had started between 3 and 6 weeks (Figure 9) and had continued until at least 9 weeks after implantation (Table 5). 3.4. Discussion In the present study we added nano–sized apatite into low molecular weight polylactide and obtained relatively homogenous composites with various apatite contents. We observed that the solvent–based manufacturing method did not alter the properties of the polymer (i.e. molecular weight) and it is not expected it would influence on the chemistry of both polymer and apatite. All implants of 0% CaP, 10% CaP and 20% CaP collapsed within 12 weeks in vivo, while 40% CaP retained its three–dimensional porous shape. Interestingly, the implants containing the higher percentage of calcium phosphate apatite particles induced bone formation following intramuscular implantation. Since this phenomenon was shown in an ectopic implantation site, this can be defined as osteoinduction. [221] 61
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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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Chapter 5 - Al lkali surface treaat
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Chapter 5 - Alkali surface treatmen
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Chapter 6 - Fluid uptake as instruc
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Chapter 6 - Flu uid uptake as insst
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Figure 7. Mass left (a) annd fluid
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Chapter 7 - Polymer molecular weigh
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ūapatite = 100 · mdry · pap Chap
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Chapter 7 - Polymer mole ecular wei
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CHAPTER 8 General discussion
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Chapter 8 - General discussion can
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Chapter 8 - General discussion cons
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Chapter 8 - General discussion 8.1.
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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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