In 3D printing it is necessary to use materials with superior shear-thinning and recovery properties, such as Gellan Gum (GG) However, this polymer lacks the biological cues necessary to develop a bioactive ink. To address this matter, the aim of this work was to incorporate extracellular matrix (ECM) components into GG and investigate cellular response to different hydrogels formulations, envisioning applications in the development of cell-specific bioinks.
Human dermal fibroblasts (hDFBs) were cultured for 21 days in culture medium supplemented with 50 μg/ml ascorbic acid. An already established protocol based on freezing/thawing was followed to extract the maximum amount of the ECM produced. Extracts were combined with GG to form hydrogels that were further crosslinked with PBS or culture medium. An array of formulations of GG/ECM with several polymer and ECM ratios were produced. Matrix and polymer content ranged from 1% to 5% (w/v) and 0.75% to 1.25% (w/v), respectively. GG was used as control. Preliminary results demonstrated the possibility to conjugate components from hDFB’s ECM to GG, obtaining stable gels under in vitro conditions for up to 14 days. During this timeframe, proteins released from the gels were quantified by Bradford Protein Quantification Assay. A gradual release of protein content occurred within the first 7 days, while the structural integrity of the gels was maintained. Regarding cell studies, 1 x 104 hDFBs were encapsulated within the gels, and their cytocompatibility was assessed by Live/Dead and Phalloidin/DAPI staining. Good cell viability was observed in all formulations and cytoskeletal staining showed that the amount of ECM components determines cell adhesion and morphology. These results confirmed the proposed hypothesis of an ECM-dependent responsiveness of cells towards the material, conferring biological cues to this shear-thining hydrogel with potential to develop a bio-tailored bioink.
Acknowledgments: FCT/MCTES PD/BD/135248/2017; FCT Doctoral Program in Tissue Engineering, Regenerative Medicine and Stem Cells PD/00169/2013; and Consolidator Grant Project “ECM_INK” (ERC-2016-COG-726061).
| 
