Cell-laden printed hydrogel scaffolds with glutamic acid-modified hyaluronic acid/collagen concentration gradients...

Biomimetic gradients are desirable features for hydrogel to improve their similarity to the three-dimensional cell culture environment. However, gradient hydrogel scaffolds for simulating heterogeneous tissue to regulate brain neural stem cells (NSCs) fate remain underexplored. Hydrogel scaffolds with concentration gradients were prepared by light-curing printing, guiding brain NSCs directional migration. Directional migration reasons are systematically discussed. Exploiting the hydrolytic stability and biocompatibility of glutamate (Glu) grafted onto polymers, hyaluronic acid (HA) was functionalized with Glu to synthesize HA-Glu with 25.5 % substitution. Scaffold materials comprised gelatin methacryloyl (GelMA), sodium carboxymethyl cellulose (NaCMC), HA-Glu, and collagen (Col). SEM revealed that HA-Glu and Col formed an interpenetrating polymer network (IPN), superimposing vascular-like fibrillar Col and brain-mimetic lamellar HA-Glu. Rheological analysis confirmed hydrogels achieved rapid photo-crosslinking within 75 s, reducing UV-induced cellular damage. The compression modulus was tunable via HA-Glu/Col content while maintaining water uptake, enabling mechanical differences. Gradient hydrogels with different HA-Glu/Col concentration regions were constructed in 2D/3D directions. Cell viability exceeded 85 % in each region, excluding the effect of cell death on migration. The gradient hydrogels could directionally guide cellular migration toward the 4HA-Glu/4Col region. This work provides practical insights into developing gradient hydrogel scaffolds for multilayer neural tissue engineering.