Block Polyelectrolytes Scaffolds Enable 3D Printing of Gelatin Inks at Physiological Temperatures

Rapid prototyping of computer-aided 3D printing of cells is expected to open great avenues in the field of tissue engineering. However, efforts to meet the growing need for biomaterials that act as 'bioinks' for 3D bioprinting are hindered due to the poor mechanical properties of most bioinks. In this contribution, we demonstrate the utility of block polyelectrolyte (bPE) additives to enhance the viscosity and resolve longstanding challenges with three-dimensional printability of extrusion-based biopolymer inks. The addition of oppositely charged bPEs into solutions of photocurable gelatin methacryloyl (GelMA) results in complexation-driven self-assembly of the bPEs, leading to GelMA/bPE inks that are printable at physiological temperatures, representing stark improvements over GelMA inks that suffer from low viscosity at 37 °C leading to low printability and poor structural stability. Hierarchical microstructures of the oppositely charged bPE self-assemblies (either jammed micelles or three-dimensional networks), confirmed by small angle X-ray scattering, is attributed to the enhancements in the shear strength and printability of the GelMA/bPE inks. Varying bPE concentrations enabled facile tuning of the rheological properties to meet the criteria for pre- and post-extrusion flow characteristics for 3D printing. Furthermore, bPE self-assemblies enhance the shear strength of photocrosslinked GelMA hydrogels – photocrosslinked GelMA/bPE hydrogels exhibit higher shear strength than GelMA hydrogels. Moreover, we show the printability assessment of GelMA/bPE inks which indicate excellent two- and three-dimensional printing performance.