Ionically crosslinked hydrogels

Finally, a new water-soluble polyphosphazene was recently synthesized that has the structure shown in 36 (46). This polymer has two attributes as a biomedical macromolecule. First, the pendent carboxylic acid groups are potential sites for condensation reactions with amines, alcohols, phenols, or other carboxylic acid units to generate amide, ester, or anhydride links to polypeptides or bioactive small molecules. Second, polymer forms ionic crosslinks when brought into contact with di- or trivalent cations such as Ca or Ai3+. The crosslinking process converts the water-soluble polymer to a hydrogel, a process that can be reversed when the system... 

Allcock, H. R., and Kwon, S., An ionically-crosslinkable poly-phosphazene Poly[di(carboxylatophenoxy)phosphazene] and its hydrogels and membranes. Macromolecules. 22. 75, 1989. 

Berger J, Reist M, Mayer JM, Felt O, Peppas NA, Gurny R. Structure and interactions in covalently and ionically crosslinked chitosan hydrogels for biomedical applications. European Journal of Pharmaceutics and Biopharmaceutics 2004, 57, 19-34. 

Poultice is a drug-in-adhesive type of TDS and is very popular in Eastern countries. The hydrogel PSA is a base adhesive for poultice, as well as for skin care cosmetic sheets. A hydrogel adhesive is an ionically crosslinked polyacrylic acid swelling in a water-glycerin mixture. In addition, poultice formulation also... 

There are four methods of gelation that can be employed to generate crosslinked hydrogel formats. The first method, which was aUuded to earlier, is ionic crosslinking induced by divalent cations like calcium. In the presence of calcium, the multiple guluronate units in the alignate polymer chain form... 

Hydrogel n A three-dimensional network of a hydrophilic polymer, generally covalently or ionically crosslinked. The most widely used example is poly (hydroxyethyl methacrylate), especially in medical applications such as implants, blood bags, and syringes. 

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