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

Chapter 5.
Characterization <strong>of</strong> Scaffolds for Connective Tissue Engineering
SCION ® image analysis <strong>of</strong> SEM micrograph was done for each condition. No macro pores were
observed for sample A1 due to high dP/dt, A4 due to low T sat . For <strong>the</strong> o<strong>the</strong>r samples in A2, A5, A6, A8,
A10, A11 and A12 macro pores had average diameter above 275m. A13 had maximum macro pores <strong>of</strong>
diameter 298 m along micro and meso pores. It was quite difficult to maintain 35 o C <strong>of</strong> temperature during
<strong>the</strong> experimentation. Because <strong>of</strong> temperature variations, we had to repeat <strong>the</strong> experiments thrice to attain T sat ,
data <strong>of</strong> all <strong>the</strong> samples were recorded for calculations and analysis.
Figure 5.33 and Figure 5.34 reveal that samples A3 and A9 produce pores <strong>of</strong> diameter ~200μm
while samples with higher macro pore diameter produced cell density above 1×10 3 , while cell densities for
micro and meso pores are also satisfactory.
Figure 5.35 compares <strong>the</strong> % <strong>of</strong> surface area <strong>of</strong> three types <strong>of</strong> pores. We can see that samples A2,
A5, A6, A7, A8, A10, A11 and A12 consist <strong>of</strong> more than 80% <strong>of</strong> surface area <strong>of</strong> macro pores produced. In
A2,A11 and A12 <strong>the</strong> percentage is above 95%. These three foams are quite close to each o<strong>the</strong>r. In o<strong>the</strong>rs
cases, <strong>the</strong>re are variations in <strong>the</strong> three types <strong>of</strong> pore distribution.
Figure 5.36 reveals <strong>the</strong> optimum values <strong>of</strong> process parameters at which pores <strong>of</strong> maximum
diameters can be produced. In our finding with PLGA 50:50 , we have found that a combination <strong>of</strong>, T sat =
37.5°C, P sat = 120 bars, t sat = 25 min, and dP/dt = 3 bar/s, produce scaffold <strong>of</strong> optimum porosity, cell density
and pore distribution.
Pore Diameter ( d e ) m
400
300
200
100
Micro Pores Pore Variation in Foam
Meso Pores
Macro Pores
Cell Density-Pores / (cm) 3
10 7 Micro Pores
Meso Pores
Macro Pores
10 6
10 5
10 4
Cell Density <strong>of</strong> Pores
0
A1
A2
A3
A4
A5
A6
A7
A8
A9
PLGA 50:50
Foams
A10
A11
A12
10 3
A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12
PLGA 50:50
Foams
Figure 5.33: Distribution <strong>of</strong> pores at different
process condition.
Figure 5.34: Cell densities <strong>of</strong> pores produced at
different process condition.
Pore Surface Area (%)
100
80
60
40
20
0
Micro Pores
Area Distribution Meso Pores <strong>of</strong> Pores
Macro Pores
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
A12
PLGA 50:50 Foams
Pore Diameter ( d e ) m
300
250
200
150
100
50
0
35
Tsat (°C)
32.5
PLGA 50:50
Optimum <strong>Parameters</strong>
37.5
Psat (bar)
110
120
130
tsat (min)
15'
20'
25'
dP/dt (bar/s)
Process Condition [T sat -P sat -t sat -dP/dt]
2
3
4
Figure 5.35: Percentage <strong>of</strong> surface area for
distribution <strong>of</strong> pores.
Figure 5.36: Effective pore diameter for each
process parameter.
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