Highly extensible physically crosslinked hydrogels for high-speed 3D bioprinting

Hydrogels have emerged as promising materials for bioprinting and many other biomedical applications due to their high degree of biocompatibility and ability to support and/or modulate cell viability and function. Yet, many hydrogel bioinks have suffered from low efficiency due to limitations on accessible printing speeds, often limiting cell viability and/or the constructs which can be generated. In this study, we report a highly extensible bioink system created by modulating the rheology of physically crosslinked hydrogels comprising hydrophobically modified cellulosic biopolymers and additives such as surfactants or cyclodextrins. We demonstrate that these hydrogel materials are highly shear-thinning with broadly tunable viscoelasticity and stress-relaxation behaviors through simple modulation of the composition of the additives. Rheological experiments demonstrate that increasing concentration of rheology-modifying additives yields hydrogel materials exhibiting extensional strain-to-break values up to 2000%. We demonstrate the potential of these hydrogels for use as bioinks by evaluating the relationship between extensibility and printability, demonstrating that greater hydrogel extensibility enables faster print speeds and smaller print features. Our findings suggest that optimizing hydrogel extensibility can enhance high-speed 3D bioprinting capabilities.