2.5.2. Bio-Ink Preparation

L929 Fibroblasts (ATCC) were loaded in the 2 wt % CMCh solution (prepared in RPMI 1640) at a 2 × 10<sup>6</sup> cells/mL concentration. Solutions of both hydrogel precursors (2 wt % CMCh loaded with L929, and 4 wt % HAox-0.4 wt % HA) were transferred into the printing syringes and two layers of square-based (120 × 120 mm<sup>2</sup> ) scaffolds were printed at r.t onto glass coverslips. The final cell concentration in the scaffold was 1 × 10<sup>6</sup> cells/mL. An additional post-printing stabilization step was carried by immersion in a 20 mM FeCl<sup>3</sup> aqueous solution for 7 min. After that time, solution was removed and samples were incubated in cell culture media.
