The Degradation and Mechanical Properties of Hydrogels

James Howard, Ryan Wade &  Dr. Jason Burdick

Our first Research Spotlight was written by James Howard, a junior working in Dr. Jason Burdick’s lab.  If you would like to learn more about his work or the other research being conducted by the Burdick lab, feel free to visit their lab website.

The goal of the research was to form a mathematical model that related the strength of hydrogels with a hyaluronic acid (HA) backbone to the enzymatic degradation rate of that hydrogel. Ultimately, this model could be used for future studies that apply to cell culturing, cell delivery, and growth factor delivery.

In degradation analysis, hydrogels were tagged with a fluorescent molecule before cross-linking, and after gelation, these gels were put in varying concentrations of Type II collagenase, which contains matrix metalloproteinases. Every other day, the gels were refreshed with collagenase or buffer, and the supernatant was collected to determine HA release from the network (fluorometric analysis). The results showed that the 4 wt% gels were mechanically stronger than the 2 wt% gels because a larger weight percent corresponds to an increase in cross-linking density, causing the gels to be stronger. The degradable hydrogels completely degraded in response to collagenase because the peptide sequences within the gel are recognized. In contrast, non-degradable gels remained intact in collagenase as the peptide cross-linkers were not recognized by collagenase.

The next step in developing this mathematical model is to measure the Michaelis-Menten degradation parameters of single degradable and non-degradable peptides to incorporate into a statistical model of degradation.