and development of polysaccharides and their derivatives as the natural materials for the removal of pollutants with different structures.
6.2.7 Textiles
The natural fibers obtained from wood, hemp, cotton, jute, and flax contain a high amount of cellulose (more than 85%) and serve as raw materials for the paper and textile industries [207]. Cellulose accounts for more than half of all the carbon found in the vegetable kingdom; thus, it is the most abundant of all carbohydrates. About 95% of cotton fibrils is cellulose. In the field of textile production, although the use of noncellulose synthetic fibers has been increasing, cotton and rayon still account for more than 70% of the fabrication [208].
Cotton (Gossypium sp.) fiber has been widely studied as the major natural fiber used in the textile industry. The fiber primary cell wall is mainly composed of cellulose, hemicelluloses, and pectins. Several of the non-cellulosic polysaccharides, such as xylan, xyloglucan and callose, appeared to be partially retained during textile processing, though they were still largely impacted by both bleaching/scouring and mercerization processes. These hemicelluloses can resist harsh treatments, possibly because they reside within the fiber structure during the textile processing treatments. Such investigations would be of the greatest value since the determination of the fates of non-cellulosic polysaccharides during the textile processing offers useful information for future functionalization studies of cotton by specifically targeting these non-cellulosic polysaccharides and for optimization of cotton treatments [209].
Textiles have undergone surface modifications to enhance their softness, absorbance, dyeability, and wettability. The latest advances in textile chemistry include surface modifications to achieve antimicrobial activity, prevent skin irritation, and even enhance the fragrance [205]. Textile fabrics offer an ideal environment for microorganisms to grow in contact with the skin of the human body, especially at appropriate humidity and temperature. Anti-microbial agents are used to preventing three undesirable effects in textiles. The first purpose is the prevention of degradation phenomena. The second purpose is the prevention of unpleasant odor and the third is the prevention of health risks [206]. Although several chemicals have been used to gain antimicrobial activity to textile products, some of these chemicals, such as formaldehyde derivatives, are toxic to the human body and do not easily degrade in the environment [205, 207]. As an alternative approach, chitosan and its derivatives have been investigated for the fabrication of antibacterial fibers to be used in textile fabrication [208]. The amino groups of the polycationic form of chitosan interact with the microbial cell walls and this interaction causes the degradation of proteins and other intracellular constituents of the microorganism. Chitosan also alters the permeability of the microbial cells, therefore induces the loss of essential nutrients and eventual death [209]. In addition, chitosan is considered to be an attractive biomaterial in the area of microencapsulation technology due to its nontoxic, biocompatible, and biodegradable nature. Recently, microcapsules have been applied to textiles to provide different added values, such as long-lasting fragrance, antimicrobial effect, and thermal regulation. The loaded microcapsules with antimicrobial agents can effectively interact with microorganisms on the skin if they are fixed on the textile product [206]. Chatterjee et al. developed chitosan microcapsules that can interact with polyester by ionic interactions and can stay on the surface of the textile substrate after several washing cycles [207]. Textile processing with the microcapsules has been also an emerging issue to achieve the real benefit of smart textiles. Textile processing with biopolysaccharide-based microcapsules to repel mosquitos is one of the revolutionary innovations in the textile industry [208]. To obtain long-duration protection from mosquitoes using insect repellent N, N-diethyl-m-toluamide (DEET), Fei and Xin incapsulated DEET in situ during the graft copolymerization of butyl acrylate onto chitosan in an aqueous solution. The obtained aqueous emulsions were applied to cotton textiles by spraying. Treated cloth has been shown high bactericidal activity, but also mosquito repellency activity even after 48 h of exposure to air [210]. Hydrogels were also aimed to design smart textile materials, such as being pH-sensitive, temperature-sensitive, and temperature/pH dual-sensitive. However, some challenges of developing smart textile materials are still needed to be overcome; for example there is a need for the development of techniques for successful attachment of the hydrogel layer to the textile substrate [211].
In textile production, polysaccharides are also used for textile printing as a thickener. Textile printing is the process of applying color to textile substrate in defined patterns or designs. It is a “localized dyeing” method in which the colors are restricted to the design areas on the printed textile. For printing of textile substrate with reactive dyes; natural thickeners or modified natural thickeners are typically used as thickening agents to prevent the color from spreading to unwanted areas. Sodium alginate and guar gum are widely used for cotton printing [212].
The textile industry is looking for environmentally friendly processes as alternatives to toxic textile chemical usage. It is expected that natural polysaccharide-based innovative strategies will enable creating of new generation textile materials, which not only contain fibers with advantageous and conventional properties but also with advanced and ecofriendly functionalities.
6.3 Conclusion
A large number of biologically active polysaccharides are available with varying structural and biological activities. Unique physicochemical and biological characteristics of natural polysaccharides, together with biocompatibility, renewability, and nontoxicity properties, make them ideal candidates for applications in many different fields including health, environment, food, and energy. However, despite the favorable features of polysaccharide-based materials, there are still drawbacks to overcome. For instance, there is a risk that a natural polysaccharide may cause the overactivation of the immune system due to its heterogeneous complex structure, insufficient level of chemical and biological purity and/or manufacturing processes. Besides, the composition of many natural polysaccharides can vary depending on the season, population age, species and geographical origin. Also, many challenges are faced during the purification and modification steps of polysaccharides, especially during surface modifications and assembly processes. Another challenge is the development of biopolysaccharide based composites to achieve multifunctional materials to fit several needs. Although the sophistication of this line of research has increased dramatically in recent years, still further efforts are required.
Research into polysaccharides, like proteins and nucleic acids, is one of the most important cutting-edge topics to explore life. Examination of the structural characteristics and structure–function aspects, assessment of proper purity, and development of new and sensitive methods to accurately determine the purity of isolated polysaccharides, and investigations of novel and functional modification methods to obtain functionally improved polymers are essential for further developments in polysaccharide field.
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