Chitin, Chitosan, and Alginate Fibers

Keywords

Controlled release • Antibacterial agent • Tissue engineering • Tissue engineer­ing scaffold • Biodegradation • 3D scaffold • Porous structure • Artificial nerve graft • Sensor • Actuator

26.1 Chitosan Fibers for Controlled Release Applications

Chitosan fibers were used to load silver particles by adding sodium hydrogen zirconium phosphate into the spinning solution [07Qin]. The silver particles were reported to be uniformly divided in the fibers and did not affect the color of the fibers. SEM image in Fig. 26.1 shows the presence of the nanoparticles on the surface of the fibers. Silver ions were released when the fibers were placed in water or aqueous protein solution. Incorporation of silver significantly increased the antibacterial activity of the fibers with greater than 98 % reduction for common bacteria. The ability of chitosan fibers to absorb silver and zinc ions that are delivered through wound dressings was investigated [06Qin]. Chitosan fibers were treated with silver nitrate and zinc chloride solutions, and the release of these ions in saline was studied. It was found that the silver-containing fibers had good antimicrobial properties, whereas the zinc-containing fibers could be used to deliver zinc ions for wound care applications. Figure 26.2 shows that the chitosan — and silver-containing fibers had a clear Escherichia coli inhibition compared to the viscose fiber-containing solution suggesting that the chitosan fibers inhibited bac­terial growth.

A blend of chitosan and polyethylene glycol (PEG) fibers was prepared, and the ability of the fibers to load and release salicylic acid as a model drug was studied [08Wan]. Chitosan and PEG were dissolved in acetic acid, and the two solutions were mixed to obtain 2 %, 5 %, 8 %, and 10 % PEG, and the solution was extruded into an ethanol coagulation bath containing 10 % tripolyphosphate. Two levels of salicylic acid were added onto the fibers, and the ability of the fibers to load and

release the drug was determined. The addition of PEG destroyed the close packing of chitosan molecules leading to a decrease in % crystallinity. Tensile strength and elongation of the fibers increased up to the addition of 6 % PEG and decreased at higher levels of PEG. The highest strength obtained was 1.5 g/den, and the breaking elongation obtained was 21 %. The presence of PEG was found to assist release of drug since PEG could dissolve in the release medium, but the amount of release was highly dependent on pH. In a similar approach, chitosan fibers were blended with starch (10 %, 30 %, 50 %, and 70 %) and loaded with salicylic acid. Tensile strength and elongation increased to 1.4 g/den and 24 %, respectively. With the addition of 30 % starch but decreased with higher levels of starch. Up to 100 % drug release was obtained within 1-7 days depending upon the concentration of starch in the fibers with higher ratio of starch leading to faster release [07Wan].

Fragrant chitosan fibers were prepared by suspending chitosan fibers in various types of aldehydes. Fibers produced had fineness ranging from 24 to 33 den, tenacity from 2.0 to 2.6 g/den, and elongation of 9.6-18.8 % [99Hir]. It was reported that a portion of the aldehydes was released into the air, whereas no release was observed when the fibers were closed in a glass vessel. The fragrant fibers were expected to be useful for air filters, cosmetics, textiles, and other applications.