Chitin, Chitosan, and Alginate Fibers

Keywords

Antifungal • Antimicrobial • Inhibition • Biocompatibility

The antifungal activity and cytotoxicity of zinc, calcium, and copper alginate fibers were studied to evaluate the feasibility for tissue engineering and medical applications [12Gon]. Antifungal activity of the fibers was measured against Can­dida albicans, and the cytotoxicity was measured using human fibroblast and human embryonic kidney cells. Figure 32.1 shows the zone of inhibition of the calcium (a), copper (b), and zinc alginate (c) fibers against C. albicans. As seen from the figure, zinc alginate fibers had higher inhibitory zone and rates (80 %) compared to copper (60 %) and calcium alginate (40 %) fibers. In addition, zinc alginate fibers did not show any cytotoxicity but promoted cell growth indicating the suitability of the fibers as scaffold for tissue engineering. In a similar research, copper alginate fibers with tenacity up to 2.4 g/den were developed and were reported to have good antibacterial activity [05Mik].

In addition to their medical application, alginates have also been reported to have good inherent flame retardancy. The influence of zinc ions on the thermal degradation and the flame resistance of alginate fibers were investigated [13Tia]. Alginic acid fibers prepared by washing calcium alginate fibers with hydrochloric acid were used as control. Later, the alginic acid fibers were treated with solutions containing zinc sulfate at various concentrations (4 %, 8 %, 10 %, and 25 %) at 60 °C for 2 h. Parameters that can evaluate flame-retardant behavior of the fibers with and without zinc are shown in Table 32.1. The limiting oxygen index (LOI), a simple and direct measure of flammability, is higher for fibers containing zinc compared to the pure alginic acid fibers. Materials with LOI above 27 are considered to be flame retardant which indicates that adding even 4 % of zinc was sufficient to make the fibers flame retardant [13Tia]. Other flame-retardant properties also showed that the addition of zinc makes the fibers flame retardant. In terms of thermal degradation, the addition of zinc increased the maximum

Table 32.1 Antiflammable parameters of alginic acid fibers containing various levels of zinc [13Tia]

degradation temperature to 250 °C compared to 210 °C for the fibers without any zinc.

In another research, calcium alginate fibers were claimed to be inherently flame retardant, and the thermal degradation mechanism and pyrolysis products were studied [11Zha]. Calcium alginate fibers had an LOI of 48 compared to 20 for viscose making the fibers inherently flame retardant. Upon pyrolysis, calcium alginate fibers formed thick residues that inhibited heat transfer. Also, crusts formed after burning by calcium alginate were thicker and more consistent than the crust from viscose fibers demonstrating a condensed phase activity that could inhibit smoke release. Alginate fibers produced much less smoke and formed about 32 % residue. Some of the parameters to evaluate the flame-retardant properties of calcium alginate fibers are given in Table 32.2 in comparison to viscose fibers.

References

[05Mik] Mikolajczyk, T., Wolowska-Czapnik, D.: Fibers Text East. Eur. 13(3), 35-38 (2005) [11Zha] Zhang, J., Ji, Q., Shen, X., Xia, Y., Tan, L., Kong, Q.: Polym. Degrad. Stabil. 96, 936 (2011)

[12Gon] Gong, Y., Han, G., Zhang, Y., Pan, Y., Li, X., Xia, Y., Wu, Y.: Biol. Trace Elem. Res. 148, 415 (2012)

[13Tia] Tian, G., Ji, Q., Xu, D., Tan, L., Quan, F., Xia, Y.: Fibers Polym. 14(5), 767 (2013)