3D bioprinting and in vitro study of bilayered membranous construct with human cells-laden alginate/gelatin composite hydrogels.

Extrusion-based 3D bioprinting of cell-laden hydrogels is a potential technology for regenerative medicine, which enables the fabrication of constructs with spatially defined cell distribution. However, the limited assessment of rheological behaviors of hydrogel before printing is still a major issue for the advancement of 3D bioprinting. In this work, we systematically investigated the rheological behaviors (i.e. viscosity, storage modulus (G'), and loss modulus (G")) of alginate/gelatin composite hydrogels first for 3D printing complex constructs. The rheological studies revealed that viscosity of alginate/gelatin hydrogels is temperature-dependent and shear thinning. Sol-gel transition (intersection of G' and G") study provided indication for printing temperature, which are in the range of 18.8 °C (H2/7.5) to 24.5 °C (H2/24.5). The alginate (2 wt%) /gelatin (15 wt%) composite hydrogel sample was chosen to print the constructs and subsequent bioprinting. Complex constructs (i.e. nose and ear) were obtained with high printing resolution (151 ± 13.04 μm) in a low temperature (4 °C) chamber and crosslinking with 2 wt% CaCl2 subsequently without extra supports. Human amniotic epithelial cells (AECs) showed superior potential to differentiate into epithelial cells, while Wharton's jelly derived mesenchymal stem cells (WJMSCs) showed a superior angiogenic potential and fibroblastic phenotype. For the in vitro study, AECs and WJMSCs as seed cells, encapsulated in alginate/gelatin composite hydrogels, were bioprinted to form biomimetic bilayered membranous construct. High cell viability (> 95%) were observed up to 6 days after printing. The presented 3D bioprinting of human AECs and WJMSCs-laden alginate/gelatin composite hydrogels provides promising potentials for future skin tissue engineering.