3D bioprinted dynamic bioactive living construct enhances mechanotransduction-assisted rapid neural network self-organization for spinal cord injury repair.

Biomimetic neural substitutes, constructed through the bottom-up assembly of cell-matrix modulus via 3D bioprinting, hold great promise for neural regeneration. However, achieving precise control over the fate of neural stem cells (NSCs) to ensure biological functionality remains challenging. Cell behaviors are closely linked to cellular dynamics and cell-matrix mechanotransduction within a 3D microenvironment. To address this, a dynamic bioactive bioink is designed to provide adaptable biomechanics and instructive biochemical cues, specifically tailored for the fate commitment of NSCs, through incorporating reversible Schiff-base bonds and bioactive motifs, N-cadherin-mimicking and BDNF-mimicking peptides. We demonstrate that the dynamic properties of 3D bioprinted living fibers alleviate the mechanical confinement on NSCs and significantly enhance their mechanosensing, spreading, migration, and matrix remodeling within the 3D matrix. Additionally, the inclusion of N-cadherin-mimicking and BDNF-mimicking peptides further enhances cells' ability to sense and respond to mechanical and neurotrophic cues provided by the surrounding matrix, which accelerates the self-organization of a functional neural network within the 3D bioprinted construct, leading to significant motor and sensory function recovery in a rat complete spinal cord injury model. This work underscores the critical role of precisely designing cell-instructive bioinks for the advanced functionality of 3D bioprinted living constructs in neural regeneration.