(489d) Enzymatic and Cell-Mediated Degradation of Synthetic Hydrogel Scaffolds Measured Using Passive Microrheology

Synthetic scaffolds are designed to be remodeled and degraded by migrating cells for applications in tissue engineering, wound healing and stem cell culture. Although the starting material properties can be meticulously designed, as cells interact with the scaffold little is known about how the rheological properties and microenvironments evolve. Measuring these dynamic changes in rheological properties, even in the absence of cells, have proven to be difficult especially in the area directly around the cell, the pericellular region. In this work, we use multiple particle tracking microrheology (MPT) to measure the enzymatic and cell-mediated degradation of a synthetic hydrogel scaffold. In MPT, one micron fluorescently labeled probes particles are embedded into the precursor solution and the Brownian motion of these particles is related to rheological properties using the Generalized Stokes Einstein Relation. The hydrogel system consists of a four-arm star poly(ethylene glycol) (PEG) end functionalized with norbornene that is cross-linked with a matrix metalloproteinase (MMP) degradable peptide and a nondegradable linear PEG dithiol. The material is first degraded enzymatically, as a model system for cell-mediated degradation, and the evolving properties are measured through time and as degradability is varied. Next, we measure cell-mediated degradation during migration of human mesenchymal stem cells (hMSCs). We find that cells remodel and degrade their environment changing the structure of the gel as far as 200 µm away from the cell. Hydrogel remodeling is also measured after cells are treated with MMP and myosin II inhibitors, changing the mechanism of cell motility and, in turn, the remodeling and degradation of the scaffold. These measurements will identify rheological properties during cell-mediated remodeling of hydrogels and enable manipulation of material properties during hydrogel engineering to improve tissue regeneration.