Novel technique to control inner and outer diameter of calcium-alginate hydrogel hollow microfibers, and immobilization of mammalian cells

Calcium-alginate hydrogel hollow microfibers have a potential to be utilized in various fields such as tissue engineering. In this study, we developed a new technique for exquisite control of inner diameter (id) as well as outer diameter (od) of the microfibers using a coaxial triple cylinder. Aqueous solutions of dextran (core solution), sodium alginate (sample solution) and CaCl2 (sheath solution) were extruded simultaneously from the inner, intermediate and outer cylinders, respectively. The ratio of id to od could be controlled only by the ratio of flow volume of core solution to total flow volume of core and sample solutions (core volume ratio). The od depended on core volume ratio, flow velocities of core and sample solution at the tip of the intermediate cylinder, tip id of intermediate cylinder and flow velocity of sheath solution. Two types of mammalian cells could be separately located in the hollow core and the gel part of the microfibers. We confirmed that the cell-enclosing process scarcely influenced the viability of the enclosed cells. Although we did not perform long-term culture of the cell-enclosing microfibers in this study, these results indicate that our system has a high potential to fabricate biomimetic scaffold for tissue-engineered tubular tissues.