Photocrosslinked poly(γ-glutamic acid) hydrogel for 3D bioprinting

In this study, tyramine-modified poly(?-glutamic acid) (?-PGA/Tyr) was synthesized to fabricate a photocrosslinked ?-PGA hydrogel for 3D bioprinting. The Tyr moiety was successfully introduced into ?-PGA at different degrees of substitution (DS) ranging from 13.4 to 53.8%, as determined by 1H NMR spectroscopy. The gelation time of ?-PGA/Tyr conjugate decreased with increasing DS of Tyr in the presence of Ru2+/sodium persulfate initiators. The optimum photoinitiation conditions for the gelation of ?-PGA/Tyr conjugate at the concentration of 12 wt% and DS of 53.8% were found to be Ru2+ concentration of 0.5 mM, and sodium persulfate of 40 mM, resulting in the highest mechanical strength of the ?-PGA/Tyr hydrogel. The crosslinking density, molecular weight between crosslinks, and mesh size of the ?-PGA/Tyr hydrogel calculated using the FloryRehner equation agreed with the rheological and mechanical properties of the hydrogel. The cytotoxicity and proliferative ability of ?-PGA/Tyr hydrogels with a DS, 53.8% were found to be excellent through live/dead and WST-1 assay. Finally, a lattice structure of the ?-PGA/Tyr hydrogel (DS, 53.8%) blended with cellulose nanofibrils was successfully fabricated via 3D bioprinting.

Automated summary

In this study, a tyramine-modified poly(γ-glutamic acid) was synthesized for 3D bioprinting of a photocrosslinked hydrogel. The gelation time decreased with increasing tyramine substitution, and the optimal photoinitiation conditions were found to be Ru2+ concentration of 0.5 mM and sodium persulfate of 40 mM. The mechanical properties of the hydrogel were in agreement with the crosslinking density and molecular weight between crosslinks. The cytotoxicity and proliferative ability of the hydrogel were excellent, and a lattice structure was successfully fabricated via 3D bioprinting.