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What Caging Force Cells Feel in 3D Hydrogels: A Rheological Perspective
Giuseppe Ciccone1, Oana Dobre1,2, Graham M Gibson3
1Division of Biomedical Engineering, James Watt School of Engineering, University of Glasgow, Glasgow, G12 8LT, UK.
Advanced Healthcare Materials
|July 23, 2020
Summary
Accurate hydrogel stiffness measurement is crucial for understanding cell behavior. This study reveals conventional methods overestimate stiffness, proposing microrheology and nanoindentation for cell-scale mechanical property determination.
Area of Science:
- Biomaterials Science
- Cell Biology
- Rheology
Background:
- Hydrogel mechanical properties significantly influence cell fate, including stem cell differentiation and behavior.
- A precise correlation between hydrogel stiffness and cellular responses remains elusive in scientific literature.
- Understanding these mechanics is vital for developing biomaterials for regenerative medicine and tissue engineering.
Purpose of the Study:
- To investigate the viscoelastic properties of poly(ethylene-glycol) (PEG)-based hydrogels across various length scales.
- To identify accurate methods for measuring hydrogel stiffness that reflect the cellular microenvironment.
- To establish a reliable methodology for assessing hydrogel mechanical constraints relevant to cells in 3D cultures.
Main Methods:
- Rheological measurements were conducted on poly(ethylene-glycol) (PEG)-based hydrogels.
- Compressional deformation tests were performed to assess bulk stiffening effects.
- Passive-video-particle-tracking (PVPT) microrheology and nanoindentation were employed for cell-scale measurements.
Main Results:
- Poly(ethylene-glycol) (PEG)-based hydrogels exhibit significant stiffening under compressional force, potentially overestimating stiffness by tenfold compared to bulk measurements.
- This observed stiffening is hypothesized to result from an induced "tensional state" within the gel network.
- Passive-video-particle-tracking (PVPT) microrheology and nanoindentation accurately determine hydrogel stiffness at the cellular length scale without externally applied forces.
Conclusions:
- Conventional bulk rheology may inaccurately represent hydrogel stiffness experienced by cells.
- Passive-video-particle-tracking (PVPT) microrheology and nanoindentation offer superior accuracy for measuring cell-relevant hydrogel mechanics.
- This work provides a validated methodology for determining linear viscoelastic properties crucial for cell-material interactions in 3D hydrogel environments.
