Influence of the Processes Parameters on the Properties of The ...

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Chapter 5. Characterization <strong>of</strong> Scaffolds for Connective Tissue Engineering PLGA 85:15 (RG 858 S) is a poly (D, L-lactide-co-glycolide) with a D,L-lactide : glycolide molar ratio <strong>of</strong> 83-87 : 13-17 and initially it was white to <strong>of</strong>f-white solid fibres. PLGA 85:15 (DL-PLG) is a poly(D,L-lactide-co-glycolide) with a D,L-lactide : glycolide molar ratio <strong>of</strong> 85:15. It is white to <strong>of</strong>f-white solid. PLGA 50:50 (PLG 8523) is a poly(L-lactide-co-glycolide) with a L-lactide : glycolide molar ratio <strong>of</strong> 50:50. It is white to light tan granules. PLGA 85:15 (PLG 8531) is a poly (L-lactide-co-glycolide) with a L-lactide : glycolide molar ratio <strong>of</strong> 84:16. It is white to light tan granules. PLGA 85:15 (RG 857 S) is a poly (L-lactide-co-glycolide) with a L-lactide: glycolide molar ratio <strong>of</strong> 82-88 : 12-18 and initially it was white to <strong>of</strong>f-white granules. L-lactide co glycolide were difficult to convert in powder form due to higher modulus <strong>of</strong> L-lactide contents, while copolymers containing D,L-Lactide were easily converted into powder. PLGA 50:50 (RG 504) is a poly (D,L-lactide-co-glycolide) with a D,L-lactide : glycolide molar ratio <strong>of</strong> 48:52 to 52:48 and initially it was white to <strong>of</strong>f-white solid. PLGA 50:50 (PDLG 5010) is a poly(D,L-lactide-co-glycolide) with a D,L-lactide : glycolide molar ratio <strong>of</strong> 52:48, It is white to light tan granules. They have been purchased from BOEHRINGER Ingelheim (Germany), LACTEL (USA), GALACTIC (Belgium) and PURAC (Ne<strong>the</strong>rlands) (cf. Table 5.1). Table 5.1: Polylactide origin and physical state. Origin Biopolymer Physical state GALACTIC P L,D LA (PABR L 68) Amorphous BOEHRINGER P L,DL LA (Resomer ® LR 704) Semi Crystalline BOEHRINGER PLGA 85:15 (Resomer ® RG 858S) Amorphous LACTEL PLGA 85:15 (DL-PLG) Amorphous PURAC PLGA 50:50 (PLG 8523) Semi Crystalline PURAC PLGA 85:15 (PLG 8531) Semi Crystalline BOEHRINGER PLGA 85:15 (LG 857 S) Amorphous BOEHRINGER PLGA 50:50 (Resomer ® RG 504) Amorphous PURAC PLGA 50:50 (PDLG 5010) Amorphous Some <strong>of</strong> <strong>the</strong> polymers were initially in powder form while o<strong>the</strong>rs were in granules by source. Amorphous polymers were easy to ground in <strong>the</strong> knife mill and <strong>the</strong>y had mean size distribution ~150 m but those which were semi-crystalline took longer time and <strong>the</strong>ir mean particle size increased as <strong>the</strong> crystallinity increased (agglomeration). Granulometry <strong>of</strong> <strong>the</strong> polymer powder analysis after different time <strong>of</strong> grinding is presented in Figure 5.1. The mean size distribution <strong>of</strong> each polymer is presented in Table 5.2. To prevent degradation, polymers have been stored at 4°C in <strong>the</strong>ir powder-like form. - 114 -
Chapter 5. Characterization <strong>of</strong> Scaffolds for Connective Tissue Engineering Table 5.2: Mean diameters <strong>of</strong> <strong>the</strong> polymers after knife mill grinding by granulometry. Polymer d (50) (m) Polymer d (50) (m) P L,D LA (PABR L 68) 161.5 PLGA 85:15 (PLG 8531) 166.1 P L,DL (LA LR 704) 389.5 PLGA 85:15 (LG 857 S) 506.4 PLGA 85:15 (RG 858 S) 99.7 PLGA 50:50 (RG 504) 89.5 PLGA 85:15 (DL-PLG) 167.7 PLGA 50:50 (PDLG 5010) 178.2 PLGA 50:50 (PLG 8523) 207.7 Volume (%) 20 P L,D LA PAB RL 68 18 P L,DL LA LR 704 16 PLGA 50:50 RG 504 14 PLGA 85:15 PDLG 5010 12 10 8 Poly (Lactide-co-glycolide) : Granulometry 6 4 2 0 0.01 0.1 1 10 100 1000 10000 Particle Size(m) Volume (%) 10 Poly (Lactide-co-glycolide) PLGA 85:15 RG 858 S : Granulometry 8 6 PLGA 85:15 PL PLG PLGA 85:15 PLG 8523 PLGA 85:15 PDLG 8531 PLGA 85:15 LG 857 S 4 2 0 0.01 0.1 1 10 100 1000 10000 Particle Size(m) Figure 5.1: Size distribution <strong>of</strong> various PLAs and PLGAs after knife mill grinding. 1.1.1 Experiments on Polylactide Powders by Viscosimetry. As example, we present in detail results obtained with PLGA 50:50 (RG 504) in solution in CCl 4 at 25°C. Variation <strong>of</strong> efflux times with <strong>the</strong> polymer concentration and corresponding viscosity values are reported on Table 5.3, where t o is <strong>the</strong> flow time <strong>of</strong> pure chlor<strong>of</strong>orm and t is time for polymer solution in <strong>the</strong> Ubbelohde apparatus type 3C. C (g/dl) Average Time t (sec) Table 5.3: Viscosity values <strong>of</strong> PLGA 50:50. Relative Specific Reduced Viscosity Viscosity Viscosity rel = t/t o sp =(t - t o )/t o red = sp /C Inherent Viscosity ln rel /C 0.00 129.65 1.00 0.00 − − 0.50 172.78 1.33 0.33 0.67 0.57 1.00 226.65 1.75 0.75 0.75 0.56 1.50 295.23 2.28 1.28 0.85 0.55 2.00 359.98 2.78 1.78 0.89 0.51 Variations <strong>of</strong> efflux times with polymer concentration (C) and reduced specific viscosity ( sp ) and inherent viscosity (ln rel /C) were plotted and from <strong>the</strong> graph <strong>the</strong> point <strong>of</strong> intersection <strong>of</strong> reduced viscosity and inherent viscosity at <strong>the</strong> Y-axis gives <strong>the</strong> intrinsic viscosity [] = 0.60. By using <strong>the</strong> Mark-Houwink Relationship (MHR) KM a with K = 5.43.10 -4 dl/g and a = 0.73, we obtain: M = 14 756 g/mol. Commercial Sodium hyaluronate, or Hyaluronic acid (HA) is commonly its sodium salt form. It was purchased from Javene, France. Viscosity given by <strong>the</strong> supplier in <strong>the</strong> data sheet is 2.4- 3.2 m 3 /kg, molecular weight 2.0-3.0×10 6 Dalton and measured intrinsic viscosity as per procedure is [] = 2.92. By - 115 -
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Institut National Polytechnique de
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pleased I was to work with all memb
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Publications and Conferences The wo
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Nomenclature and Abbreviations Abbr
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