Abstract: 3D printing has made remarkable progress in soft tissue reconstruction enabling the custom design of complex material implants with patient specific geometry. The aim of this study was to inkjet print mechanically reinforced biocompatible hydrogels. Here, we developed a double crosslinked ink by optimizing the rheological properties of solutions of sodium alginate (NaAlg), NaAlg/transglutaminase (TG), CaCl2 and gelatin/CaCl2. The results showed that a two-component ink system comprising NaAlg (4% w/v)/TG (0.8% w/v) and gelatin (4% w/v)/CaCl2 (3% w/v) gave optimum printability. The mechanical and biological properties of printed alginate/gelatin hydrogels prepared from inks with different gelatin contents, and incorporated fibroblasts, were characterized by Scanning Electron Microscope (SEM), mechanical testing and laser confocal microscopy. The compressive moduli of alginate/gelatin hydrogels could be adjusted from 19.2 kPa ± 1.2 kPa to 65.9 kPa ± 3.3 kPa by increasing the content of gelatin. After incubation for 7 d, fibroblasts had permeated all printed hydrogels and the rate of proliferation increased with increasing gelatin content. The highest cell proliferation rate (497%) was obtained in a hydrogel containing 4.5% (w/v) gelatin. This study offers a new strategy for the fabrication of 3D structures used to mimic the function of native tissues.

Key words: biofabrication, inkjet printing, double crosslinking ink, mechanical and biological properties, hydrogel preparation