Photoresponsive Peptide and Polypeptide Systems. 13. Photoinduced Cross-Linked Gel and Biodegradation Properties of Copoly(l-lysine) Containing ε-7-Coumaryloxyacetyl-l-lysine Residues

Abstract

Copoly[LysLys(Cou)] containing e-7-coumaryloxyacetyl-l-lysine [Lys(Cou)] residues were synthesized by the N-carboxyanhydride method. When the aqueous solutions of copoly[LysLys(Cou)] containing 5−10 mol % of Lys(Cou) are irradiated by light, the photo-cross-linking reaction proceeds slowly between coumarin moieties in the side chains to give a cis head-to-head cyclocoumarin, and after 6−24 h the solutions become transparent hydrogels. The gels exhibit solvent-induced reversible expansion and contraction behavior in water and in ethanol. The biodegradation of the hydrogels by some proteolytic enzymes and soil filamentous fungi has been investigated using photo-cross-linked copoly[LysLys(Cou)] gels. The photo-cross-linked copoly[Lys90-95Lys(Cou)10-5] gels are degradable by trypsin and protease type XXIII or two microorganisms, Aspergillus oryzae and Penicillium citrinum, suggesting potential for a controlled biodegradation by the different cross-linking densities in the gel matrixes upon the controlled irra...