Chitosan anion binding

Chitosan for oral administration to humans is generally recognized as safe. In vitro, chitosan has been reported to bind bile acids The role of the accompanying anion is important for instance chitosan orotate salt has enhanced capacity for bile acids [11,264-267]. 

It is not surprising, therefore, that chitosan and its basic derivatives will complex with anionic dyes. Giles et al. [68,69] researched the use of chitosan for the removal of dyes from effluent as long ago as 1958. The binding capacity of chitosan for anionic dyes is pH-dependent, but it has been reported [65] that in effluent treatment as much as 10 g dye per kg chitosan can be complexed at pH values above about 6.5. Similarly, chitosan has been used for the aftertreatment of direct dyeings on cotton to improve their fastness. 

The complexing of chitosan and its basic derivatives with anionic substances is paralleled by compatibility with cationic and nonionic compounds. Similarly, the anionic derivatives of chitosan show complex formation with cationic agents and are compatible with anionic and nonionic compounds. The capability of these chitosan derivatives to complex with certain metal ions, notably those of the transition series, is also important, having possibilities for the removal of metal salts from effluent. The hierarchy in terms of binding capacity is Cr(III) < Cr(II) < Pb(II) < Mn(II) < Cd(II) < Ni(II) < Fe(II) < Co(II). 

Chitosan owes its broad-spectrum antimicrobial property to the amino groups present on the chain[17] (Figure 3.7). This implies that the %DD and MW affects this property but only a few studies [18] have tried to explain its relationship. There are two main mechanisms that have been suggested to explain the action of chitosan against microbial cells a) electrostatic membrane binding and b) cell nucleus permeation. The first mechanism is due to the interaction of chitosan s cationic amino groups with the anionic groups on the surface of microbial cells. This interaction creates a layer around the cell wall that inhibits... 

Thiolated polymers, also termed thiomers, are conventional mucoadhesive polymers chemically modified to contain a cysteine residue in the polymer chain and thus establish covalent disulfide bonds with mucin." They can be manufactured to be either cationic (mostly thiolated chitosans) or anionic (carboxylic acid-containing polymers) however, their mucoadhesive extent will mostly be determined by their capacity to covalently bind to mucin. The polypeptide backbone of mucin can be divided into three major subunits tandem repeat array, carboxyl-, and amino-terminal domains. While the amino-terminal domain contains some of the cysteine residues, the carboxyl-terminal domain contains more than 10% of the cysteine residues. These cysteine-rich regions are responsible for forming the large mucin oligomers and ultimately, the groups that allow for the covalent mucoadhesive bond formation with oral mucosal systems." ... 

Chitosan/day nanocomposites represent an innovative and promising class of materials. Potential biomedical applications of chitosan/clay nanocomposites include the intercalation of cationic chitosan in the expandable aluminosilicate structure of the clay is expected to affect the binding of cationic drugs by anionic clay the solubility of chitosan at the low pH of gastric fluid may decrease the premature release of drugs in the gastric environment ... 

Chitin, a polysaccharide-based material, is present in the shells of such sea creatures as shrimps and crabs. Chitin is biodegradable by nature, and when acetyl groups i.e. CH3-CO, are removed from the chitin molecules, chitosan is produced with exposed amine groups. The antimicrobial capabilities of chitin/chitosan are based on its cationic nature, which is capable of binding with anionic pathogens and making them ineffective (Aranaz et a/.,2009,p203). 

Chitosan, a widely used natural biopolymer, has been studied for the adsorption of various metal ions from dilute solutions. Unfortunately, the inherent properties of chitosan, such as hydrophilicity and metal-binding capability, are often insufficient to meet the requirements of a number of applications. To improve these properties, both chemical and physical modifications of chitosan are required. Thus, Aliquat 336-functionalized chitosan as adsorbent was prepared. In fact, the new chitosan adsorbent can also be described as P-SIL containing quaternary ammonium ionic liquid [23]. Unlike the previous reported structure, the Aliquat 336-functionalized chitosan, which was prepared by acid/base neutralization reaction, consists largely of cations and anions (Fig. 5.12). The structure was so flexible that the adsorption ability could be controlled precisely. Moreover, incorporation of Aliquat 336 into the chitosan backbone could significantly enhance its metal ions extraction ability. It has been shown to have much improved affinity for Pb " than pure chitosan. This may be explained in that the new strategy doesn t reduce the original amino active sites besides, the synergistic effect between cation and anion also contributes to the enhancement of adsorption capabilities. On the other hand, the effort to increase selectivity of the adsorbent for one metal ion over others is to make the adsorbent sterically efficient with that metal ion only. The new chitosan-... 

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