Page 228 - Biodegradable Polyesters

206 8 Systematic Development of Electrospun PLA/PCL Fiber Hybrid Mats

8.7
TCH Drug Release

PLA/15% HMW PCL at a blend ratio of 1/1 using chloroform/methanol cosol-
vents were only selected to examine TCH drug release and subsequent fiber
biodegradability due to produced homogeneous fibers and better PLA and
PCL miscibility when compared with other cosolvent systems. Furthermore,
the variation in the degree of crystallinity between PLA/15% HMW PCL and
PLA/9% HMW PCL was another reason to study that effect.
The drug molecules tend to attach to fiber surfaces owing to their highly ionic
interactions as well as rapid solvent evaporation from PLA/HMW PCL blend
solutions during electrospinning. Apparently observed from Figure 8.9, PLA/15%
HMW PCL fiber mats cause a slower drug release rate than PLA/9% HMW PCL
counterparts, most likely resulting from the lower fiber porosity from the higher
PCL concentration to decrease the overall detachment of TCH molecules on the
porous surfaces. The small diameters of PLA/9% HMW PCL fibrous structures
also contribute to the increase of surface areas, leading to short distances of drug
diffusion with fast TCH release.
The other point worth noting is that drug release occurred initially from the
amorphous regions [75], in good accordance with Table 8.3 in which PLA/9%
HMW PCL fiber mats show lower degree of crystallinity than PLA/15% HMW
PCL counterparts. Such low crystallinity level can facilitate the improvement of
fiber degradability and further influence the long-term TCH release.

100

90
80
Cumulative release (%) 60 70
70

50
60
50
40
30
30 Cumulative release (%) 40
20
20 10
PLA/9% HMW PCL/ TCH 0
10 PLA/15% HMW PCL/ TCH 0 0.5 1 1.5 2
Time (h)
0
0 50 100 150 200 250
Time (h)

Figure 8.9 TCH release profiles from PLA/9% HMW PCL and PLA/15% HMW PCL using
chloroform/methanol.