Hyaluronic Acid-based Inks for Stereolithography (Bio)printing: Benefits of Thiol-ene vs. Acrylate Functionalized Inks

Abstract

Hydrogel inks used for 3D bioprinting are mainly based on radical polymerization of methacrylate groups. Inks based on the radical thiol-ene polymerization have raised attention in recent years, as they are not susceptible to oxygen inhibition and require lower light doses for polymerization, therefore, they can be more benign to living cells. Here, we modified hyaluronic acid inks with allyl ether or norbornene groups, which can form a crosslinked network in the presence of a dithiol crosslinker. We performed systematic studies to compare precursor stability, photocrosslinking and printability of the thiol-ene inks with methacrylated hyaluronic acid inks. Our results showed higher storage stability of the thiol-ene hydrogel precursors over 15 months. Photorheology experiments demonstrated faster photocrosslinking and higher temporal control over the network formation in thiol-ene inks. The suitability of thiol-ene inks was demonstrated using digital light processing-based printing with a minimum print time of 2 s per layer and a xy resolution of 100 µm.