Tunable Degradation and Release Profile of Bioresponsive Gelma-Crosslinked Poly(HEMA-co-HPMA) Hydrogels

Introduction: Degradable polymer hydrogels are widely used as cell scaffolds as they provide an interactive environment for cells to attach and proliferate. For this purpose, a hybrid hydrogel was synthesized from HEMA and HPMA (synthetic) and crosslinked with GelMA (natural). This study reports on the development to this hybrid hydrogel with tunable degradation rate and release kinetics dependent on GelMA crosslinker concentration.

Materials and Methods: Poly(HEMA-co-HPMA) hydrogels were synthesized with varying mol% of GelMA and crosslinked by UV exposure. The hydrogels were characterized using FTIR, SEM, DSC, and mechanical testing. Degradation kinetics were studied by temporal mass loss. The gradual release of pre-loaded 40 kDa FITC-dextran (1 mg/mL) from the degrading hydrogels was monitored.

Results and Discussion: Poly(HEMA-co-HPMA) hydrogels have water content and Young’s modulus similar to tissue (80-85% and 0.1-1 kPa, respectively for neural tissue). The degree of hydration of hydrogels of 0.1 and 1.0 mol% GelMA, was 84 and 82% with Young’s modulus of 0.67 and 1.4 kPa, respectively. Similarly, changing the crosslinker concentration allowed for a tunable degradation rate. The percentage of mass that remained after 50 days of incubation in collagenase was, 58 and 51% for the hydrogels crosslinked with 0.1 and 1.0 mol% GelMA, respectively. Release data showed that at such low concentrations of GelMA, release was dependent on both diffusion and enzymatic degradation rather than solely on diffusion. After 24 h, the amount of 40 kDa FITC-dextran released from 0.1 and 1.0 mol% GelMA crosslinked hydrogels was ~ 2-fold more than the amount released from the same hydrogel in PBS, indicating the role of enzymatic degradation in the bio-erosive release of dextran.

Conclusions: GelMA can be used as an inexpensive, biodegradable crosslinker to yield an enzymatically degradable hydrogel with tunable physiological properties to target a wide range of applications in tissue and regenerative engineering.