Facile Fabrication of Hollow Hydrogel Microfiber via 3D Printing-Assisted Microfluidics and Its Application as a Biomimetic Blood Capillary.

Simulating the structure and function of blood capillaries is very important for an in-depth insight into their role in the human body and treatment of capillary-related diseases. Due to the similar composition and structure, hollow hydrogel microfibers are well-recognized as potential biomimetic blood capillaries. In this paper, we report a novel, facile, and reproducible method to fabricate coaxial microfluidic chips via 3D printing-assisted soft lithography and then hollow hydrogel microfibers using the as-prepared coaxial microfluidic chips. Instead of traditional photoresist-based lithography, 3D printing of gelatin hydrogel under various extrusion pressures is used to construct sacrificial templates of coaxial microfluidic chips. Various solid and hollow hydrogel microfibers with complicated and hierarchical structures can be obtained via multitype coaxial microfluidic chips or a combination of coaxial microfluidic fabrication and post-treatment. The as-formed hollow hydrogel microfibers are evaluated in detail as biomimetic blood capillaries, including physicochemical and cytological properties. Our results prove that the hollow hydrogel microfibers exhibit excellent mass transport capacity, hemocompatibility, semipermeability, and mechanical strength, and their barrier function can be further enhanced in the presence of endothelial cells. Overall, our 3D printing-assisted fabrication strategy provides a new technique to construct microfluidic chips with complicated 3D microchannels, and the resulting hollow hydrogel microfibers are promising candidates for blood capillaries.