5. Conclusion

the medium [18]. The release profiles of TB from dye loaded coaxial fibers in SBF for up to

The whole release time period varied for different types of fibers including alginate, chitosan and the core-sheath fiber depending on the period over which they could resist the media before their structure fell apart [1]. As noted previously, calcium alginate could be easily degraded when used for in-vivo applications due to the ionic exchange between the divalent cations and sodium in the which are present in the body environment [11, 18]. Therefore, it is believed that the release of TB observed from alginate fibers was mainly due to the degradation of alginate fibers. On the other hand, wet-spinning of chitosan fiber is needed to be done in basic coagulation bath which is not an appropriate condition for most of loaded drugs. Coaxial fibers indicated a controlled manner of release more or less like chitosan fibers. However, with the help of coaxial spinning, their fabrication process via wet-spinning is performed in a neutral coagulation bath. These results provide the suitable condition to load any types of drugs into the wet-spun fibers for drug delivery applications. As can be seen in Figure 12, the coaxial fibers showed similar release behavior to that of the chitosan fibers. However, they could

withstand the media for a shorter period of time without losing the initial structure.

In the initial period of 2 h, a fast release of TB from alginate fibers is observed at which more than 70% of TB is released. Either chitosan or Chit/Alg coaxial fibers showed approximately 30% burst release of TB followed by a sustained release within over 5 days. While alginate fiber could not withstand the media for more than 4 days, ca. 42 and 50% of the TB is released from chitosan and Chit/Alg fibers, respectively. Figure 12 shows a good sustained-release profile of

Figure 12. Time dependent TB releasing behavior of chitosan, alginate and Chit/Alg hydrogel fibers in SBF at 37C. Inset; burst release of coaxial fibers in the first 30 min. [11] Reproduced with permission. 158 Copyright 2015, Wiley-VCH.

5 days were plotted vs. time and are demonstrated in Figure 12.

136 Hydrogels

The development and fabrication of hydrogels fibers has been carried out to evaluate their performance for drug delivery systems. The production of coaxial hydrogels fibers were successfully developed for the first time using a wet-spinning method. The morphological, mechanical, thermal and swelling properties of these fibers are discussed [1]. Enhanced mechanical properties of 260% in ultimate stress and more than 300% in the Young's modulus were observed by incorporating 1% (w v<sup>1</sup> ) CaCl2 into the chitosan core. SEM micrographs of the cross-section of chitosan-alginate fibers clearly show the cylinder shaped monofilament form of the chitosan fiber covered with alginate. These biofibers as delivery platforms have demonstrated great potentials toward advancing current drug delivery systems. Hybrid Chit/ Alg fibers could likely be promising as a novel kind of 3D bioscaffolds in drug release studies or tissue engineering [1].
