Pure Chitosan Microfluidic Spinning Affords Modular Core‐Sheath Fibers and Hand‐Crafted Scaffolds with Enhanced Fibroblast Compatibility

Microfluidic-spun hydrogel fibers are appealing for tissue engineering and cell transplantation applications, as they give access to fiber-shaped tissues that mimic blood vessels, muscle fibers, or neural networks in vivo. Alginates are overwhelmingly employed as their base material, as they allow for simple processing, despite their poor cell adherence and weak cell-matrix interactions. Alginates also require crosslinking, and thus can leach ions and lose integrity under physiological conditions. To overcome these limitations, we are reporting herein the first synthesis of pure chitosan fibers by microfluidic wet spinning, avoiding the use of crosslinking agents, and achieving excellent cell viability of 85%. These fibers exhibit higher mechanical strength (695 MPa) than alginate counterparts (2-4 MPa). Our system can also accommodate a core of chitin nanocrystals to modulate mechanical properties or serve as a reservoir of bioactive molecules, such as methylene blue. As chitosan is a natural biopolymer, this work addresses the United Nations Sustainable Development Goals (UN SDGs) 6 and 14. The resulting pure chitosan and chitin/chitosan composite fibers exhibit high processability and can be woven into a variety of structures. Finally, these microstructured chitosan fibers have the potential to be used as templates to create fiber-shaped tissues or to develop into live building blocks for the assembly of very complex artificial tissues.