The implants are hydrogel structures that can be rapidly 3D printed into different sizes and shapes, making them easily customizable to fit the precise anatomy of a patient's spinal cord injury. Researchers fill the implants with neural stem cells and then they are fitted, like missing puzzle pieces, into sites of spinal cord injury. New nerve cells grow and axons—long, hair-like extensions through which nerve cells pass signals to other nerve cells—regenerate, allowing new nerve cells to connect with each other and the host spinal cord tissue.

"Using our rapid 3D printing technology, we've created a scaffold that mimics central nervous system structures. Like a bridge, it aligns regenerating axons from one end of the spinal cord injury to the other. Axons by themselves can diffuse and regrow in any direction, but the scaffold keeps axons in order, guiding them to grow in the right direction to complete the spinal cord connection," said co-senior author Shaochen Chen, professor of nanoengineering at the UC San Diego Jacobs School of Engineering and faculty member of the Institute of Engineering in Medicine at UC San Diego.

"In recent years and papers, we've progressively moved closer to the goal of abundant, long-distance regeneration of injured axons in spinal cord injury, which is fundamental to any true restoration of physical function," said Tuszynski.