Chitosan dependence

Since the colonic bacterial enzymes are capable of hydrolyzing various di- and oligosaccharides (glycosidases) and polysaccharides (polysaccharidases), the chi-tosanolytic activities of rat cecal and colonic enzymes on chitosan was investigated. The results revealed that the rat bacterial enzymes have the ability to degrade chitosan, depending on both the Mw and DA of the chitosan sample [171]. 

Among all the quatemized chitosans described into literature, W,W,W-trimethyl chitosan chloride (TMC) is the most widely applied for gene therapy applications [28, 33, 34]. The quatemization maintained and improved the muco-adhesive properties of chitosan, depending on the quatemization degree, which makes this chitosan derivative an ideal candidate for gene delivery [23]. Typically, TMC can be synthesized by reaction of chitosan with methyl iodide in the presence of sodium hydroxide into A-methyl-2-pyrrolidinone at 60 °C. In a second step, the iodide ion is substituted by chloride by an ion exchange process [34] (Fig. 2). 

Antimicrobial activity of chitosan depends on type of chitosan, degree of polymerization, molecular weight, pH and solvent -Chitosan nanoparticles could exhibit superior antimicrobial effect against various micro-organism than chitosan itself -The unique character of chitosan nanoparticles for their positive charge and small particle size is responsible for their potential antibacterial activity and acceptable biocompatibility... 

Almost all functional properties of chitosan depend on its chain length, charge density, and charge distribution. Numerous studies have demonstrated that the salt form, molecular weight, and degree of deacetylation of chitosan, as well as the pH at which the chitosan is used, influence the functional properties of this polymer (Kean and Thanou, 2010]. 

The molecular weight of chitosan is another important property that determines its suitability for a particular application. It determines the viscosity of its solution and the strength of chitosan fiber and film. The molecular weight of chitin and chitosan depends on its source and deacetylation conditions [time, temperature, and concentration of NaOH], respectively [1, 4]. Molecular weight of chitosan determined by various methods such as viscometry [28], gel permeation chromatography [29] and light scattering spectrophotometry [30]. 

It is widely accepted that the k and o values for chitosan depend on its DDA. Several studies have measured the k and a values for chitosans with different DDA using the same solvent systan [60,64]. Wang et al. determined k and a for chitosans with four different DDA and further generalized the relationships between k and DDA and a and DDA where DDA is expressed as percentage ... 

Moreover, Crestini et al. (1996) reported that the yields of chitosan, viz., 120mg/L of fermentation medium under liquid fermentation conditions, and 6.18g/kg of fermentation medium under solid-state fermentation conditions are produced from the mushrotxn, L. edodes. Based on this data, it can be conad-ered that the cultivation of mushroom on solid support, which is the natural growing method of mushroom, might be the best cultivation method for the production of chitin and chitosan from mushrooms. The yield of extracted chitin and chitosan depends on mushroom species, harvesting time, and chitin and chitosan extraction processes and conditions (POchanavanich and Suntomsuk 2002, Yai and Man 2007a). 

Chemical shifts or wave numbers are characteristic of particular molecular environments (Colquhoun and Goodfellow 1994). Chemical shift of particular resonance or wave number of particular absorption band varies by changing the distribution of two co-monomer units of chitin/chitosan, depending on the nature of the neighboring units (Schanzenbach and Peter 1997). 

Chitosan has been widely used for many biomedical applications because of its favorable characteristics such as biodegradability (Struszczyk et al. 1991), biocompatibility (Chandy and Sharma 1990, Hirano et al. 1990), inexpensiveness, and nontoxicity. However, the level of toxicity of the chitosan depends on the molecular weight and the degree of deacetylation. Hirano and Knapezk et al. has reported that chitosan has low oral toxicity with an LDjq in rats of 16g/kg, which is close to that of salt or sugar (Hirano et al. 1990, Knapezk et al. 1984). Chitosan is also bioactivite and bioadhesive compared with other natural polymers commonly used in drug delivery. It has antacid and antiulcer properties that prevent or weaken drug irritation in the stomach (Kumar 2000). 

The efficiency of adsorption of Hg by chitosan depends upon the period of treatment, the particle size, initial concentration of Hg, and quantity of chitosan. McKay et al. (1989) used chitosan for the removal of Cu +, Hg, Ni, and Zn within the temperature range 25°C-60°C at near neutral pH. Further adsorption parameters for the removal of these metal ions were reported by Yang and Zall (1984). Maruca et al. (1982) used chitosan flakes of 0.4-4 mm for the removal of Ci + from wastewater. 

Over the years, researchers have developed an array of methods for the preparation of chitin and chitosan, depending upon the natural source used for its procurement as well as the temperature reached during the conversion reaction. 

Contrary to chitin, chitosan is a relatively soluble biopolymer. The solution properties of a chitosan depend on its average DD and the distribution of the acetyl gronps along the main chain [146]. Various solvents and processes for spinning chitosan fibers have been developed [138, 147, 148]. In recent years, chitin/chitosan fiber spinning process and their novel applications have been continnously studied. 

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