Abstract: Methacrylated gelatin(GelMA) is a modified gelatin with photosensitive functional groups and has good biocompatibility which is used to construct soft tissue scaffolds such as skin and nerves. However, GelMA hydrogel only UV photocrosslinked has too poor mechanical properties and structural maintenance to construct three-dimensional scaffolds through extrusion-based bioprinting. This study proposes a kind of GelMA composite hydrogel consisting of GelMA, gelatin and sodium alginate which can be extruded and obtained the enhanced mechanical properties. The component ratio of GelMA composite was be determined suitable for extrusion printing through the viscosity test. The process parameters of printing pressure, nozzle moving speed, nozzle height and illumination conditions on extrusion continuity and microfilament diameter were further investigated by 3D printing experiments. When the noozzle with the inner diameter of 200 μm is used, the uniform and smooth filaments (φ293-1 211 μm) of GelMA composite hydrogel can be achieved with the process parameter ranges:the air pressure is 0.05 MPa to 0.25 MPa, the printing speed 1 mm/s to 15 mm/s, the nozzle height 200μm to 600 μm, light intensity 76 mW/cm² to 272 mW/cm². The Young's modulus of GelMA composite hydrogel has been found doubled of that of the GelMA hydrogel under the same UV crosslinking conditions(76 mW/cm²,5 min) with the same concentration(5%,w/v)in the tensile test. Good biocompatibility of GelMA composite hydrogel has been verified by the cell culture in which the survival rate of human dermal fibroblasts embedded reached 85% on day 7.

Key words: GelMA, composite hydrogel, 3D extrusion-based bioprinting, NHDFs