Micro-Mechanical Viscoelastic Properties of Crosslinked Hydrogels Using the Nano-Epsilon Dot Method

Area of Science:

• Biomaterials Engineering
• Tissue Engineering
• Biomechanics

Background:

• Developing in vitro biomimetic organ models requires engineering materials that replicate native tissue mechanical properties.
• Current research often focuses on hydrogel stiffness, neglecting their crucial viscoelastic (time-dependent) behavior.

Purpose of the Study:

• To characterize the micro-mechanical viscoelastic properties of crosslinked hydrogels at cell-relevant length scales.
• To investigate the impact of crosslinker concentration on hydrogel viscoelasticity.

Main Methods:

• Utilized nano-indentation tests with the nano-epsilon dot method on gelatin hydrogels.
• Analyzed hydrogels crosslinked with varying concentrations of glutaraldehyde (GTA).
• Fitted experimental data to a Maxwell Standard Linear Solid model.

Main Results:

• Increased GTA concentration led to higher instantaneous and equilibrium elastic moduli.
• Higher GTA concentrations also resulted in a longer characteristic relaxation time.
• Crosslinking density influences both elastic and viscous behaviors of hydrogels.

Conclusions:

• Hydrogel viscoelasticity significantly changes with crosslinker concentration, shifting towards more elastic behavior.
• Cellular responses attributed solely to substrate stiffness may be confounded by uncharacterized viscoelastic effects.
• A comprehensive understanding of both elastic and viscous properties is essential for designing effective biomimetic materials.