Chitosan-based microcapsules

Interesting properties are obtained with chitosan-based microcapsules (Skin-tex [7] Cognis). Chitosan is a biodegradable, weak cationic polysaccharide which is obtained by extensive deacetylation of chitin, a polysaccharide common in the shells of shrimps. Chitosan exhibits excellent film-forming ability, and is an excellent polymer suitable for shells. The protective chitosan layer protects the contents from warmth, drying out, and cold, and this results in durability against the wear and tear of day-to-day hfe. 

The ingredients in chitosan-based microcapsules are released through two mechanisms. First, if the microcapsule is pressed, crushed or rubbed, the core explodes and emerges. Second, the chitosan layer is slowly reduced over time through the action of the body s own enzymes this activates the ingredients and enables them to move from the fabric into the skin, thereby refining their structure (Fig. 7.3a). 

Alonso, D., Gimeno, M., Sepulveda-Sanchez, J.D., Shirai, K., 2010. Chitosan-based microcapsules containing grapefruit seed extract grafted onto cellulose fibers by a non-toxic procedure. Carbohydrate Research 345, 854—859. 

Another medical appUcalion of biopolymer-based microcapsules was reported by Hui et al. (2013). It was shown that a cotton fabric with embedded chitosan-sodium alginate (CSA) microcapsules loaded with traditional Chinese herbs, PentaHerbs, could be potentially used in the treatment of atopic dermatitis. The active ingredient used was gallic acid. The drug release from the chitosan-sodium alginate microcapsule was tested in vitro, under two simulated human skin conditions, in phosphate buffer saline (PBS) of pH 5.4 and 5.0. Fig. 5.12 demonstrates the fast release of gallic acid... 

Recent research has explored various chitosan based microencapsulated nanoparticles for circumventing various problems of conventional delivery systems. One beautiful example of chitosan-alginate PEC microcapsules by membrane emulsification method is mentioned in Fig. 3.10. 

To accelerate healing of 2,4,6-trinitrobenzenesulphonic acid-induced colitis in rats, chitosan microcapsules loaded with the anti-inflammatory drug, 5-aminosalycylic acid (5-ASA), have been evaluated in Japan [41]. In conclusion, several research groups deal with development of chit-osan-based microparticles with entrapped insulin as peroral delivery systems [42,43]. 

Figure 21.10. Microfluidic "lab on chip" design for the high throughput generation of multiple nested polysaccharide microcapsules based on the design published by. Modifications are made to enable adequate flow of alginate and chitosan solutions through the channels. Determination of channel diameters, the position of junctions and channel substrate will need to be optimized.

Hybrid hydrogels based on chitosan and Pluronics have also shown thermo-responsive properties and exhibited superior hemostatic properties (Chung et al, 2005). Microfluidics were used by Wei et al (2011) to prepare pH-responsive microcapsules based on PDMAEMA. The cationic microcapsules obtained exhibited pH-sensitivity, and the preparation conditions significantly affected their pH-responsive swelling. 

The major advantage of enzyme responsive polymers is that they do not require an external trigger. For instance, polymer systems based on alginate/chitosan or DEXS/chitosan microcapsules are responsive to chitosanase [126]. On the other hand, azo-aromatic bonds are sensitive to azo-reductase [127]. These enzymes, naturally produced by bacteria principally located in the colon, are capable of degrading polysaccharides like pectin, chitosan, amylase/amylopectin, cyclodex-trin and dextrin [120,125, 165]. 

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