Barbieri Thesis - BioMedical Materials program (BMM)

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Chapter 2 – The role of gels in instructive putties When histomorphometrically compared to the controls, significantly less bone was formed in ALG and CHI putties (p=0.043 and p=0.041 respectively), while bone formation in CMC and PLU–based putties was not significantly different from the controls (p=1 and p=0.938 respectively) (Figure 4). After 12–week implantation, CMC, PLU and ALG gels were not histologically visible in the explants. On the contrary, traces of CHI gel were still present in the samples and PVA gel still occupied most of the space between BCP granules (Figure 5). When bone formed, it was found on the surface of the ceramic in both the controls and putties (Figure 5). Osteoblasts were seen on the outer surface of the newly formed bone indicating that after 12 weeks bone formation was still active (Figure 5). Once the gels did not occupy the available space between the granules, bone formed and well–developed blood vessel networks could be observed without any detectable difference amongst the putties (Figure 5). Under fluorescent microscopy, calcein (green, week 3) and xylenol orange (red, week 6) were detected in all the samples that induced bone formation. In particular, calcein was observed on BCP granules (in both controls and putties) while xylenol orange was seen on the newly formed bone (Figure 6), indicating that the process of bone formation started between 3 and 6 weeks after implantation. 2.4. Discussion The possibility to develop osteoinductive mouldable materials has been assessed in this study. We used five potential polymer binders, chosen basing on their history of use in pharmaceutical and medical fields (Table 1). The ability of the gels to retain ceramic granules was studied first, and then their biocompatibility and effects on the osteoinductive potential of BCP granules have been evaluated with an animal study. The importance of surface micro–structure on osteoinduction of calcium phosphate ceramics has already been shown in several studies. [86, 228, 236, 237] The results herein presented show that once a polymer binder covers the surface of micro–structured BCP for a period longer than two weeks in vitro (i.e. PVA gel), osteoinduction does not occur. However, as we hypothesized, if the polymer binder can be quickly cleared by dissolution, osteoinduction of micro–structured BCP in putties may be guaranteed. We observed that the carrier component of the putties dissolved in vitro with different rates (Figure 2) loosening the BCP granules: CMC, PLU and ALG gels started to dissolve in short time (i.e. within few hours) and their putties completely lost their shape within one day, while putties containing CHI gel started to lose shape later and PVA putties kept their integrity up to 14 days. During histology analysis, we could not detect any trace of CMC, PLU and ALG gels in their harvested putties, while traces of CHI gel were occasionally observed. 34
Figure 3. HHistology overvieew of the explanted putties. Bone was observed in (a) CMC putty, (b) PLU putty, (c) AALG putty, (d) CHHI putty and (f) BCP granules alonne (i.e. control). No bone could be b observed in (e) PVA putty, while remnnant PVA gel wa as still visible amoongst the granule es. The histology y staining is methylene blue/basic fuchssin where bone is dark pink/red, , soft tissues are e light violet/pink k and BCP granules arre dark brown/blaack. The gel in PV VA putty (e) is staained light pink (f for detail see Figu ure 5). Area percentage of bone (%) 30 25 20 15 10 5 0 BBCP CMC CChapter 2 – The role r of gels in innstructive puttie es PLU ALG CHI PVAA Figure 4. Histogram showwing the area percentage of boone in the differ rent groups afte er 12–week intramuscullar implantation. As compared to the controls, siggnificantly less bo one was formed in ALG and CHI puttiess (indicated by sttars), while the decrease d of bonee formation in CM MC and PLU–ba ased putties was not siggnificant. Putties containing PVA gel did not inducce bone formatio on. Statistical com mparison is expressed iin terms of p–values and is report ted in the text. 35
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INSTRUCTIVE COMPOSITES FOR BONE REG
Page 5 and 6: INSTRUCTIVE COMPOSITES FOR BONE REG
Page 7: 献给潘臻 A mamma e papà A Stef
Page 11 and 12: Summary Summary Developing new biom
Page 13: Summary containing 96%mol. L-lactid
Page 16 and 17: Samenvatting De behoefte aan een de
Page 18 and 19: Samenvatting structuur, bespoedigt
Page 20 and 21: Riassunto velocità di dissoluzione
Page 22 and 23: Riassunto generale, ha migliorato i
Page 25 and 26: Chapter 1 - Introduction 1.1. Eukar
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Chapter 4 - Conntrol of mechanical
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Chapter 4 - Control of mechanical a
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CHAPTER 5 Effects of alkali surface
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Chapter 5 - Alkali surface treatmen
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Chapter 5 - Al lkali surface treaat
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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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