Balancing Strength and Cell Viability in Gelatin Methacrylate/Gellan Gum Bioink Formulations

Soft tissue injuries resulting from trauma or degeneration are challenging to treat due to limited regenerative capacity, particularly in complex tissues, such as the central nervous system (CNS), nerves, and cartilage, where biomechanical and biochemical factors hinder effective repair. In these cases, tissue engineering presents a promising approach by combining biomaterials, cells, and bioactive signals to enhance soft tissue regeneration; however, its success relies on the compatibility between implanted materials and native tissue. Among the advances in this field, 3D bioprinting enables precise spatial control of the scaffold architecture and cell positioning, making it well-suited for developing constructs that mimic native tissue. In this study, we developed and characterized a series of bioink formulations based on a dual network system of gelatin methacrylate (GelMA) combined with gellan gum (GG). The GelMA/GG hydrogels were evaluated using rheological and compression testing as well as biodegradation and cell viability assays, including live/dead fluorescence microscopy. Formulations containing two different concentrations of GelMA (2.5 and 4.0% w/w) and GG (0.25 and 0.50% w/w) were tested, and the rheological results showed a strong dependence of the elastic component (<i>G</i>') on GG concentration. For the 2.5% GelMA formulations, increasing the GG content significantly enhanced the Young's modulus. In 4.0% GelMA formulations, stiffness increased as the GG concentration rose. Higher GG content decreased biodegradation over 14 days in phosphate-buffered saline and reduced cell viability due to the hydrogel's increased stiffness. The bioinks demonstrated suitable rheological properties for bioprinting, achieving over 98% cell viability after 1 day. Additionally, formulations such as 4.0% GelMA with 0.25% GG and 2.5% GelMA with 0.5% GG exhibited high cell viability (above 85%) when maintained even after longer culture periods, such as 14 days. These results indicate that GelMA/GG hydrogels have great potential as versatile, tunable bioinks for soft-tissue engineering in the CNS. Future research will focus on modifying the hydrogel network's rigidity to enhance cell viability further and refine its application in bioprinting strategies for regenerating soft tissues in the central nervous system.