The application of microwave heating to the synthesis of 6-amino-6-deoxycellulose

Chitosan: The One and Only? Aminated Cellulose as an Innovative Option for Primary Amino Groups Containing Polymers

The aim of this study was the synthesis and in vitro characterization of aminated cellulose as alternative excipient to chitosan. The aldehyde form of cellulose was generated via the oxidative cleavage of vicinal diols by the addition of increasing concentrations of sodium periodate. The insertion of primary amines was achieved by reductive amination with ammonia. The degree of substitution was calculated via primary amino group quantification using a 2,4,6-trinitrobenzenesulfonic acid assay. Mucoadhesiveness was examined by adopting the rotating-cylinder method and tensile studies using porcine intestinal mucosa. Hydration was evaluated at pH 2-11. The successful formation of aldehydes as well as a subsequent introduction of up to 311.61 micromoles per gram of primary amines were proven to correlate with the amount of added periodate. There was a 3- to 14-fold prolongation in the mucosal residence time of the new polymer in comparison to chitosan, as measured by the rotating-cylinder method. Although cationic cellulose did not reach the maximum detachment force of chitosan, the total work of adhesion of the newly synthesized cellulose derivate was higher than that of chitosan. The higher the degree of amination, the higher the degree of hydration in neutral and alkaline aqueous media was. Compared to chitosan, the novel cationic cellulose derivative displays improved mucoadhesive properties as well as sufficient hydration at physiological pH. Therefore, aminated cellulose is a promising alternative to the cationic polymers, such as chitosan, used thus far.

Chemical modification of polysaccharides

This review covers methods for modifying the structures of polysaccharides. The introduction of hydrophobic, acidic, basic, or other functionality into polysaccharide structures can alter the properties of materials based on these substances. The development of chemical methods to achieve this aim is an ongoing area of research that is expected to become more important as the emphasis on using renewable starting materials and sustainable processes increases in the future. The methods covered in this review include ester and ether formation using saccharide oxygen nucleophiles, including enzymatic reactions and aspects of regioselectivity; the introduction of heteroatomic nucleophiles into polysaccharide chains; the oxidation of polysaccharides, including oxidative glycol cleavage, chemical oxidation of primary alcohols to carboxylic acids, and enzymatic oxidation of primary alcohols to aldehydes; reactions of uronic-acid-based polysaccharides; nucleophilic reactions of the amines of chitosan; and the formation of unsaturated polysaccharide derivatives.