Development of soft gels printable in biocompatible structures that support cellular elongation for neural stem cells and cerebral organoids

Engineering physiologically relevant neural models requires soft, biofunctional matrices that mimic the extracellular microenvironment. Neural stem cells (NSCs) and cerebral organoids (cORGs) are particularly demanding, as they need three-dimensional (3D) environments that support elongation and maturation. However, achieving process control and long-term compatibility in 3D bioprinting remains a current challenge. A low-viscosity bioink composed of Gelatine, Sodium Alginate, Carboxymethyl cellulose and Matrigel, with a final viscosity of approximately 116 mPa·s at 119 s⁻¹, was optimized for embedded extrusion bioprinting of NSCs and cORGs. Constructs were fabricated in a gelatin bath at a speed of 20 mm/s and a controlled pressure of 0.3 bar, and printability was evaluated using a numerical index. Structural stability, viability, and neural elongation were assessed under varying crosslinking conditions. The bioink enabled reproducible constructs with sustained stability. NSCs maintained high viability but showed limited neurite elongation, depending on crosslinking. Conversely, cORGs displayed morphological maturation and upregulation of neural markers including PAX6, FOXG1, DCX, and TTR, reflecting their spatial organization. The developed bioink ensures stable, reproducible neural constructs and reveals distinct responses of NSCs and cORGs to bioprinting. While NSC differentiation was constrained, cORGs benefited from the 3D environment. These results are a step forward towards the development of neural-specific in vitro models.