Chelation Crosslinking of Biodegradable Elastomers

Abstract

Widely present in nature and in manufactured goods, elastomers are network polymers typically crosslinked by strong covalent bonds. Elastomers crosslinked by weak bonds usually exhibit more plastic deformation. Here, chelation as a mechanism to produce biodegradable elastomers is reported. Polycondensation of sebacic acid, 1,3-propanediol, and a Schiff-base (2-[[(2-hydroxyphenyl) methylene]amino]-1,3-propanediol) forms a block copolymer that binds several biologically relevant metal ions. Chelation offers a unique advantage unseen in conventional elastomer design because one ligand binds multiple metal ions, yielding bonds of different strengths. Therefore, one polymeric ligand coordinated with different metal ions produces elastomers with vastly different characteristics. Mixing different metal ions in one polymer offers another degree of control on material properties. The density of the ligands in the block copolymer further regulates the mechanical properties. Moreover, a murine model reveals that Fe³⁺ crosslinked foam displays higher compatibility with subcutaneous tissues than the widely used biomaterial-polycaprolactone. The implantation sites restore to their normal architecture with little fibrosis upon degradation of the implants. The versatility of chelation-based design has already shown promise in hydrogels and highly stretchy nondegradable polymers. The biodegradable elastomers reported here would enable new materials and new possibilities in biomedicine and beyond.

Keywords: biocompatibility; biodegradable elastomers; metal chelation crosslinking.