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

Chapter 5.
Characterization <strong>of</strong> Scaffolds for Connective Tissue Engineering
Chapter 5
Chapter
5
Characterization <strong>of</strong>
Scaffolds for
Connective Tissue
Engineering
In this chapter, we present characterization <strong>of</strong> different biopolymers such as P L LA, P L,DL LA,
PLGA 50:50 and PLGA 85:15 for a comparative study. Particular attention has been focused on amorphous and
semi-crystalline polymers. The modelling <strong>of</strong> scCO 2 foaming <strong>of</strong> polymers by pressure quench method requires
<strong>the</strong> resolution <strong>of</strong> <strong>the</strong> diffusion equation as well as <strong>the</strong> degree <strong>of</strong> depression <strong>of</strong> <strong>the</strong> glass transition <strong>of</strong> polymer
as a function <strong>of</strong> <strong>the</strong> amount <strong>of</strong> CO 2 sorbed. Indeed, certain iso<strong>the</strong>rmal sorption data and its modelling are
required for such study. In this chapter, after explaining <strong>the</strong> principles <strong>of</strong> <strong>the</strong> foaming phenomenon
precisely, we have focused on <strong>the</strong> resolution <strong>of</strong> diffusion equation, <strong>the</strong> <strong>the</strong>rmodynamics <strong>of</strong> phase equilibrium,
<strong>the</strong> depression <strong>of</strong> T g as a function <strong>of</strong> <strong>the</strong> CO 2 sorption. Finally, we have derived <strong>the</strong> nucleation equation,
which is based on <strong>the</strong> use <strong>of</strong> <strong>the</strong> classical nucleation <strong>the</strong>ory.
Then characterization <strong>of</strong> <strong>the</strong> foams obtained by supercritical CO 2 process by varying <strong>the</strong> ratios <strong>of</strong>
LA/GA contents were taken into account to correlate solubility <strong>of</strong> <strong>the</strong> scCO 2 <strong>of</strong> pellets and equivalent pore
size and porosity in scaffolds. A focus on pore morphology, structure anisotropy and <strong>the</strong>ir characteristics
will be emphasized as it plays an important role in cell seeding, differentiating and growth in <strong>the</strong> scaffold.
1 Characterization <strong>of</strong> Biomaterials
1.1 Characterization <strong>of</strong> Polylactide Powders
All <strong>the</strong> polymers in powder form were used directly by sieving through 500 m mesh to avoid any
foreign particles or agglomerate. O<strong>the</strong>rs in granules and pellet form were ground in knife mill as described
in chapter 4. The physical appearance and composition <strong>of</strong> each polymer is stated as under:
P L,D LA (PABR L 68) is L,D polylactic acid containing approximately 12% <strong>of</strong> D-lactic acid. They
are available in brownish yellow granules form.
P L,DL LA (LR 704) is a poly (L-lactide-co-D,L-lactide) with a L-lactide : D,L-lactide molar ratio <strong>of</strong>
67:33 to 73:27. It is white to <strong>of</strong>f-white granules.
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