Cross-Linker Architectures Impact Viscoelasticity in Dynamic Covalent Hydrogels

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Mechanobiology

Background:

• Dynamic covalent cross-linked (DCC) hydrogels mimic native tissue mechanics with viscoelasticity and self-healing.
• Traditional hydrogels lack the tunable mechanical properties of DCC hydrogels.
• The influence of cross-linker architecture on DCC hydrogel viscoelasticity remains underexplored.

Purpose of the Study:

• To investigate how varying cross-linker architectures affect the stiffness and viscoelasticity of hydrazone-based alginate hydrogels.
• To establish structure-property relationships for designing DCC hydrogels with specific mechanical profiles.

Main Methods:

• Synthesized alginate hydrogels utilizing hydrazone dynamic covalent chemistry.
• Varied cross-linker concentration, stoichiometry, and architecture (side-chain cross-linker (SCX), linear telechelic (LX), and star telechelic (SX)).
• Characterized hydrogel mechanical properties including stiffness and stress relaxation dynamics.

Main Results:

• SCX hydrogels: increased stiffness and slower stress relaxation with higher concentrations; reduced stiffness and faster relaxation with off-stoichiometric ratios.
• Telechelic hydrogels (LX and SX): maximal stiffness and relaxation at intermediate mixing ratios; higher valency enhanced properties.
• Distinct mechanical property ranges were achieved across architectures; SCX exhibited slower relaxation, SX showed greater stiffness and slower relaxation than LX.

Conclusions:

• Cross-linker architecture is a critical determinant of DCC hydrogel stiffness and viscoelasticity.
• Tailoring cross-linker design allows for precise control over hydrogel mechanical properties.
• These findings provide a foundation for developing advanced DCC hydrogels for regenerative medicine and mechanobiology.