Hyperbranched polymer hydrogels with large stimuli-responsive changes in storage moduli and peroxide-induced healing

Hydrogels with the ability to repair damage or undergo controllable changes in stiffness and swelling are becoming increasingly important in multiple technologies. For example, hydrogels performing as dynamic matrices are able to more accurately capture cellular processes such as fibrosis compared to static hydrogels. However, it has been suggested that changes in hydrogel stiffness of several kPa are required in order to observe meaningful differences in cell behavior. In the work reported here gels have been prepared using hyperbranched polymers containing pendent thiols. Softening experiments with these gels resulted in stiffness changes of around 8.5 kPa after a thiol-disulfide exchange reaction with a small-molecule thiol compared to only 4.5 kPa for gels made from linear polymers. The hydrogels also demonstrated healing behavior when treated with hydrogen peroxide, and healed gels with higher values of storage moduli could be obtained from using hyperbranched polymers. Collectively, these results demonstrate how polymer architecture can be used to increase the stimuli-responsiveness of synthetic hydrogels. It is anticipated that these results will be useful in in vitro models for studying cellular behavior with dynamic matrix changes.