k-Carrageenan and PVA blends as bioinks to 3D print scaffolds for cartilage reconstruction

3D printing of polymeric scaffolds and autologous stem cells is a promising tool for damaged facial cartilage reconstruction surgeries. To this end, suitable bioinks are needed to generate scaffolds with the required morphological and functional features. We formulated hydrogel bioinks using k-Carrageen (kC) and poly(vinyl alcohol) (PVA) in three different weight ratios. The kC gives the systems the ability to undergo rapid sol-to-gel transitions upon cooling from 60 °C and above to body temperature, while the PVA is used as rheology modifier and porogen. The latter is crosslinked after molding or printing by freeze-thaw cycling for 1 day (FT1) or 5 days (FT5). To select the most suitable formulation for 3D printing, the sol-to-gel transition and the physico-chemical, mechanical and morphological properties of obtained hydrogels were studied. Moreover, the absence of cytotoxic effects of the material on SASCs was assessed in both stemness-preserving or chondro-inductive media. Printing trials were performed to identify optimal process parameters and co-printing and post-printing seeding approaches of SASCs were evaluated. Cells were found to be viable after co-printing and also after the FT1 treatment. Viable adherent cells were also found in the FT5 system, where cells were plated after freezing and thawing treatment.