title: Coaxial nozzle-assisted 3D bioprinting with built-in microchannels for nutrients delivery.
abstract: This study offers a novel 3D bioprinting method based on hollow calcium alginate filaments by using a coaxial nozzle, in which high strength cell-laden hydrogel 3D structures with built-in microchannels can be fabricated by controlling the crosslinking time to realize fusion of adjacent hollow filaments. A 3D bioprinting system with a Z-shape platform was used to realize layer-by-layer fabrication of cell-laden hydrogel structures. Curving, straight, stretched or fractured filaments can be formed by changes to the filament extrusion speed or the platform movement speed. To print a 3D structure, we first adjusted the concentration and flow rate of the sodium alginate and calcium chloride solution in the crosslinking process to get partially crosslinked filaments. Next, a motorized XY stages with the coaxial nozzle attached was used to control adjacent hollow filament deposition in the precise location for fusion. Then the Z stage attached with a Z-shape platform moved down sequentially to print layers of structure. And the printing process always kept the top two layers fusing and the below layers solidifying. Finally, the Z stage moved down to keep the printed structure immersed in the CaCl2 solution for complete crosslinking. The mechanical properties of the resulting fused structures were investigated. High-strength structures can be formed using higher concentrations of sodium alginate solution with smaller distance between adjacent hollow filaments. In addition, cell viability of this method was investigated, and the findings show that the viability of L929 mouse fibroblasts in the hollow constructs was higher than that in alginate structures without built-in microchannels. Compared with other bioprinting methods, this study is an important technique to allow easy fabrication of lager-scale organs with built-in microchannels.
authors.affiliation: The State Key Lab of Fluid Power Transmission and Control, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China; Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Gao
authors.affiliation: The State Key Lab of Fluid Power Transmission and Control, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China; Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China. Electronic address: yongqin@zju.edu.cn.
authors.forename: Yong
authors.initials: Y
authors.lastname: He
authors.affiliation: The State Key Lab of Fluid Power Transmission and Control, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China; Key Laboratory of 3D Printing Process and Equipment of Zhejiang Province, College of Mechanical Engineering, Zhejiang University, Hangzhou 310027, China.
authors.forename: Jian-zhong
authors.initials: JZ
authors.lastname: Fu
authors.affiliation: Department of Orthopaedic Surgery, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310009, China.
authors.forename: An
authors.initials: A
authors.lastname: Liu
authors.affiliation: Zhejiang California International NanoSystems Institute, Zhejiang University, Hangzhou 310058, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Ma
mesh_terms: D000818:Animals; D061249:Batch Cell Culture Techniques / Q000295:instrumentation*; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D003470:Culture Media / Q000737:chemistry / Q000493:pharmacokinetics; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology*; D005434:Flow Cytometry / Q000295:instrumentation; D017022:Flow Injection Analysis / Q000295:instrumentation; D056656:Lab-On-A-Chip Devices; D051379:Mice; D066330:Printing, Three-Dimensional / Q000295:instrumentation*; D023822:Tissue Engineering / Q000295:instrumentation*
chemical_list: D003470:Culture Media
keywords: 3D bioprinting; Cell viability; Coaxial nozzle; Filament fusion