Authors:

Zhiyuan Chen

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Biodegradability is an important parameter in biomaterials design, with implications for drug delivery and tissue engineering. While various degradable polymers have been developed, precisely tuning the rate of degradation to range from days to months has been challenging. Here, we develop hyaluronic acid (HA)-based polymeric hydrogels that are chemically modified to confer hydrolytic degradability. Specifically, we hypothesized that varied amounts of dialdehyde groups on the HA backbone, in combination with covalent crosslinking via norbornene groups with enhanced susceptibility to hydrolysis, would achieve tunable degradation profiles. We used esterification and oxidation reactions to chemically modify HA to introduce norbornene (via carbic anhydride) and dialdehyde (via sodium periodate) groups, respectively. Nuclear magnetic resonance was used to verify chemical modifications. Gelation properties were determined using oscillatory shear rheology with dynamic light exposure and mechanical properties were characterized using uniaxial compression testing. The polymers were used to make microgels using a flow-focusing microfluidic device. Microgel mass swelling ratio, morphology, and degradation via release of a fluorescent label were characterized over time. Hydrogels crosslinked instantaneously on light exposure, and mechanical properties could be tuned by varying crosslinker density. We found carbic anhydride-modified hydrogels degraded after 10 days of immersion in aqueous media, whereas control hydrogels showed negligible degradation. The presence of dialdehyde groups (2.5% theoretical degree of modification) had limited effects on degradability but showed significantly greater swelling behavior. These promising findings warrant further investigation of how different degrees of oxidation, in combination with different crosslinking densities and polymer concentrations, influence hydrogel degradability. Keywords: Biodegradable; Hydrogel; Tissue Engineering; Biomaterials; Controlled Release

Source:

Purdue University / 2024

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Co-authors:

Zhiyuan Chen