Gel properties as a hydrogel of crosslinked poly (l-ornithine) using organic crosslinking agents

Gel formations of water-soluble cationic ornithine polypeptides were examined using organic aliphatic crosslinking agents such as dialdehydes and diketones in water systems. When 1/20-5 equivalent molar amounts of organic crosslinking agents were added to the ornithine polypeptide systems, the corresponding gels were formed. Among the organic crosslinking agents used, glutaraldehyde was the most effective for the gel formation. As a whole, the molecular weight of the samples, the amino acid compositions, the crosslinking agents used, the molar ratios between crosslinking agents and functional residues, and system pH levels were found to play roles in the gel formation. The gels formed were characterized by swelling properties and by the selective adsorption ability of some amino acids. The polyornithine gels exhibited reversible, but hysteretic swelling in a water-acetone mixed solvent. Due to the cationic δ-amino moieties which remain unreacted, the acidic amino acid, aspartic acid, was adsorbed into the gels' matrix, exhibiting the predominant adsorption. Biodegradable characteristics of the copoly (ornithine tyrosine) [copoly (Orn Tyr)] gels by chymotrypsin were also investigated.