Collagen fibers in neural tissue protect and support neurons, and they may also direct nerve fiber growth during development and regeneration. As a result, it is vital to guide nerve fiber orientation in vitro to ensure proper organization and connection during neural tissue engineering. Fibers produced via melt-electrowriting, electrospinning, or polymer airbrush have been used for this purpose; nevertheless, they are inefficient in creating an ECM-like soft environment for cell growth. Combining fibers with soft, cell-supportive hydrogels can address the issue.

Hydrogel-fiber composite scaffolds have emerged as a viable material for tissue engineering applications due to their unique mechanical and biological features. The hydrogel matrix, like the extracellular matrix in actual tissues, creates a three-dimensional environment that can be tailored to elicit certain biochemical signals, such as the regulated release of bioactive chemicals. The scaffold's fibrous component supports cell adhesion, alignment, differentiation, and guided tissue creation. The addition of fibers increases the scaffold's mechanical characteristics, making it more suited for a variety of tissue engineering applications. The current study aims to develop hydrogel-fiber composite scaffolds that allow for axon alignment in neural tissue engineering applications.

Due to its ease of application, no solvent requirements, and extensive tuning choices, melt-electrowriting was used to establish a foundation of PCL fibers in the micrometer range. In addition to increasing cell adhesion, we found that coating PCL fibers with gelatine and cationic BSA helped cells to align along the fiber line. These PCL microfibers were combined with alginate hydrogels containing encapsulated human-derived neuroblastoma SH-SY5Y cells at varying concentrations. High cell viability was observed post-encapsulation. In the next step, alginate-encapsulated SH-SY5Y cells are bioprinted on top of PCL scaffolds to create well-defined 3D architectures of fiber-hydrogel composite scaffolds.

In conclusion, the alignment of neurons on composite scaffolds can be a promising approach for the development of functional neural tissue. Due to the solvent free approach, meltelectrowritten PCL-alginate composite scaffolds can be helpful in promoting directional cell growth, which is an important step towards engineering neural tissue for several applications.