Internal Catalysis in Dynamic Hydrogels with Associative Thioester Cross-Links

Area of Science:

• Biochemistry
• Polymer Chemistry
• Materials Science

Background:

• Thioesters are crucial in biosynthesis and are utilized as reactive handles in chemical biology.
• Thioester exchange reactions typically require catalysts or high pH conditions for acceleration.

Purpose of the Study:

• To investigate the use of bifunctional aromatic thioesters as dynamic covalent cross-links in hydrogel networks.
• To understand the mechanism and kinetics of thioester exchange at physiological pH in aqueous environments.

Main Methods:

• Synthesis and characterization of bifunctional aromatic thioesters.
• Fabrication and mechanical testing of hydrogels cross-linked with these thioesters.
• Kinetic studies of transthioesterification and macromolecular stress relaxation measurements.

Main Results:

• Demonstrated that transthioesterification occurs at physiological pH in aqueous conditions, facilitating stress relaxation within hundreds of seconds.
• Identified intramolecular hydrogen bonding as the key factor accelerating thioester exchange.
• Showcased tunable stress relaxation properties in hydrogels without compromising network stiffness.

Conclusions:

• Bifunctional aromatic thioesters can serve as effective dynamic covalent cross-links in hydrogels.
• Intramolecular hydrogen bonding significantly accelerates thioester exchange, enabling dynamic network behavior.
• This system offers a pathway to engineer materials with adaptable mechanical properties through associative dynamic cross-links.