Polysaccharide reactive cross-linkers

Biopolymer capsules have been prepared via non-covalent interactions between various biopol3mrers and bromoisobutyramide surface-functionalized templates [73]. These authors proposed that the adsorption of the biopolymer was achieved through non-covalent halogen bonding (Fig. 13.6). Enzymes, proteins, polypeptides, polynucleotides, and polysaccharides have been used for preparation of the capsules. Their mechanical stabihty has been improved by cross-linking with an amine reactive cross-linker [74] or via repeated refimctionalization of the deposited layer/biopolymer adsorption [75]. 

The carbonyl-reactive functional group on these cross-linkers is a hydrazide group that can form hydrazone bonds with aldehyde residues. To utilize this functional group with carbohydrate-containing molecules, the sugars first must be mildly oxidized to contain aldehyde groups by treatment with sodium periodate. Oxidation with this compound will cleave adjacent carbon—carbon bonds that possess hydroxyl groups, as are abundant in polysaccharide molecules (Chapter 1, Sections 2 and 4.4). 

Applications for separation membranes are many and diverse separation membranes must also function in a variety of conditions. For example, when hydrophilic or hydrophobic membrane materials are desired, they can be easily synthesized because chitin and chitosan have many reactive functional groups, such as hydroxyl and amino groups. These reactive groups are useful for the introduction of functional groups and cross-linkers, and consequently function to strengthen and improve separation membranes. Since chitin and chitosan are polysaccharides derived from... 

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