Chitin Nanoparticles

Chitin (Fig. 3.1) is also a biopolymer that is abundant in nature. It is isolated from crab, shrimp, and lobster shells as a byproduct of the seafood industry. Worldwide, several million tons of chitin are generated annually as waste by the seafood industry. Chitin has been successfully prepared by several methods such as enzymatic methods, methods using hydrolytic conditions of boiling HCl and vigorous stirring, and methods using chitin whiskers of slender parallelepiped rods. Previous research has reported the preparation of presumably functional chitin nanoparticles and their 

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Li, Q., Zhou, J.P., Zhang, L.N. J. Polym. Sci.Part B Starch-based composites reinforced with novel chitin nanoparticles. Polym. Phys. 47, 1069-1077 (2009)... 

In their work, (Chang et al. 2010b, c) found that the incorporation of chitin nanoparticles imiformly dispersed in a starch matrix at low loading levels (till 5 wt %) led to improvements in mechanical parameters (tensile strength, elastic modulus, and Tg) and water vapor permeability. For higher filler contents, agglomeration occurred, but good interfacial interactions between the nanofiller and the starch could be observed. 

Chang PR, Jian R, Yu J, Ma X (2010b) Fabrication and characterisation of chitosan nanoparticles/ plasticised-starch composites. Food Chem 120 736-740 Chang PR, Jian R, Yu J, Ma X (2010c) Starch-based composites reinforced with novel chitin nanoparticles. Carbohydr Polym 80 421 26... 

The addition (loading) of nanomaterials to polymers leads to significant changes in their physical, mechanical as well as thermal properties. Due to the hierarchical stmcture and semicrystalline nature of polysaccharides (cellulose, starch, and chitin), nanoparticles can be extracted from these naturally occurring polymers (Dufresne 2010). 

Chang, P.R., Jian, R., Yu, J., and Ma, X. (2010) Starch-based composites reinforced with novel chitin nanoparticles. Carbohydrate Polymers,... 

Dev, A., Mohan, J. C., Sreeja, V., Tamura, H., Patzke, G. R., Hussain, F., Weyeneth, S., Nair, S. V., Jayakumar, R. Novel carboxymethyl chitin nanoparticles for cancer drug delivery applications. Carbol r Polym 2010,79,1073-1079. 

One of the most applicable additives are nano-Ag particles, which are incorporated or deposited onto nanofibres here are listed a few examples. Ifiiku et al. (2015) reported the use UV light for the reduction of silver ions deposited on chitin nanofibre surfaces. Silver nanoparticles endowed strong antifungal activity to the chitin nanofibres in a study in which the effect of AgN03 on the nanofibre diameter and... 

Ifuku, S., Tsukiyama, Y., Yukawa, T., Egusa, M., Kaminaka, H., Izawa, H., Morimoto, M., Saimoto, H., 2015. Facile preparation of silver nanoparticles immohilized on chitin nanofiber surfaces to endow antifungal activities. Carbohydrate Polymers 117, 813—817. 

For the purpose of chitosan nanoparticles preparation, 20 mg chitosan is dissolved in 40 ml of 2.0 % (v/v) acetic acid and 20 ml of 0.75 mg/ml tripolyphosphate TPP is dropped into a beaker at room temperature. After that chitosan solution was sonicated for 5 min and centrifuged for 15 min at 6000 rpm in order to obtain chitosan nanoparticles. These chitosan nanoparticles could be stored in distilled water however, sonication for 10 s should be applied before a further immobilization step. The morphological characterization of the chitin whisker and chitosan nanoparticles can be evaluated by a Transmission Electron Microscopy (TEM) and Nanosizer. 

As previously mentioned, natural fibres present a multi-level organization and consist of several cells formed out of semi-crystalline oriented cellulose micro fibrils. Each microfibril can be considered as a string of cellulose crystallites, linked along the chain axis by amorphous domains (Fig. 19.10) and having a modulus close to the theoretical limit for cellulose. They are biosynthesized by enzymes and deposited in a continuous fashion. A similar structure is reported for chitin, as discussed in Chapter 25. Nanoscale dimensions and impressive mechanical properties make polysaccharide nanocrystals, particularly when occurring as high aspect ratio rod-like nanoparticles, ideal candidates to improve the mechanical properties of the host material. These properties are profitably exploited by Mother Nature. 

Compared to cellulose or chitin, the morphology of constitutive nanocrystals obtained from starch is completely different. Figure 19.12 shows a TEM obtained from a dilute suspension of waxy maize starch nanocrystals. They consist of 5-7 nm thick platelet-like particles with a length ranging 20-40 nm and a width in the range of 15-30 nm. The detailed investigation on the stmcture of these platelet-like nanoparticles was reported [36]. 

As chitosan is versatile, it can be manufactured into films, membranes, fibers, sponges, gels, beads, and nanoparticles, or supported on inert materials. The utilization of these materials presents many advantages in terms of applicability to a wide variety of process configurations. The various forms of chitin and chitosan are discussed below. 

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