Paper Number
PO11 

Session
Poster Session

Title
Determination of macroscopic rheological properties of human mesenchymal stem cell laden poly(ethylene glycol) hydrogels

Presentation Date and Time
October 11, 2017 (Wednesday) 6:30

Track / Room
Poster Session / Cripple Creek Ballroom

Authors (Click on name to view author profile)

1. Mazzeo, Michelle S. (Lehigh University, Bioengineering)
2. Schultz, Kelly M. (Lehigh University, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Michelle S. Mazzeo¹ and Kelly M. Schultz^2
1Bioengineering, Lehigh University, Bethlehem, PA 18015; ²Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015

Speaker / Presenter 
Mazzeo, Michelle S.

Text of Abstract
Developing hydrogels that harness human mesenchymal stem cells’ (hMSCs) natural tendency to migrate to wound sites and regulate healing produce implantable scaffolds that enhance wound healing and prevent the development of critical wounds. By studying the material’s structure and rheological properties, we can develop hydrogels that withstand necessary stresses and maintain high cellular viability. In our work, our hydrogels, which consist of 4-arm star poly(ethylene glycol) (PEG) functionalized with norbornene and a matrix metalloproteinase (MMP) degradable peptide sequence, use thiol-ene click chemistry for 3D hMSC encapsulation. MMPs are cell-secreted enzymes that degrade the peptide cross-linker sequence. This enables cells to shape their microenvironments during basic cellular processes, such as motility. Unlike biological scaffolds, synthetic PEG hydrogels do not provide unknown complex biological cues, providing a well-defined environment to study cell-material interactions. Therefore, this work characterizes the macroscopic material properties of these hydrogels using bulk rheology, in order to optimize hydrogel design and improve its effectiveness as a wound healing material. Hydrogel stiffness is monitored as it affects cell motility. As cells degrade the scaffold, the storage moduli decreases more than twofold within the first 24 to 48 hours after cell encapsulation. Hydrogels without cells have larger storage moduli than hydrogels with cells at a given time, indicating cell laden scaffolds are degraded by cell-secreted enzymes. Additionally, viability assays show that cell viability remains high for extended periods of time within the hydrogel, and cells survive stresses applied from the rheometer. By determining material properties and cell viability over extended periods of time, these macroscopic rheological findings can be combined with microscopic rheological results to design hydrogels that are optimized for increasing the rate of wound healing.