Fabrication of cell-compatible hyaluronan hydrogels with a wide range of biophysical properties through high tyramine functionalization
Enzymatically mediated crosslinked hyaluronan–tyramine hydrogels (HA–Tyr) are promising matrices for tissue engineering and regenerative medicine. However, due to relatively low tyramine modifications of the hyaluronan backbone achieved, HA–Tyr matrices have a weak and narrow range of mechanical properties. The iterative use of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) as a coupling agent increased the yields of tyramine functionalization, which was reflected by a two-fold increase in Young's modulus of HA–Tyr hydrogels. The accurate control over hydrogel degradation was also facilitated. Viable encapsulation of human mesenchymal stem cells, with 85–98% over 6 days, was achieved in all hydrogels and distinct cellular spreading was observed in the absence of additional binding cues. The biophysical properties of the tunable HA–Tyr hydrogels are improved to study a wide range of cellular behaviors.