Biobased hydrogel bioinks of pectin, nanocellulose and lysozyme nanofibrils for the bioprinting of A375 melanoma cell-laden 3D in vitro platforms

Melanoma is one of the most aggressive types of skin cancer, and the need for advanced platforms to study this disease and to develop new treatments is rising. 3D bioprinted tumor models are emerging as advanced tools to tackle these needs, with the design of adequate bioinks being a fundamental step to address this challenging process. Thus, this work explores the synergy between two biobased nanofibers, nanofibrillated cellulose (NFC) and lysozyme amyloid nanofibrils (LNFs), to create pectin nanocomposite hydrogel bioinks for the 3D bioprinting of A375 melanoma cell-laden living constructs. The incorporation of LNFs (5, 10 or 15 wt%) on a pectin-NFC suspension originates inks with enhanced rheological properties (shear viscosity and yield point) and proper shear-thinning behavior. The crosslinked hydrogels mimic the stiffness of melanoma tissues, being stable under physiological and cell-culture conditions, and non-cytotoxic towards A375 melanoma cells. P-NFC-LNFs (10 %) reveals good printability (Pr = 0.89) and printing accuracy (51 ± 2 %), and when loaded with A375 cells (3 × 10⁶ cells mL^-1) the bioink originates 3D-constructs with high cell viability (92 ± 1 %) after 14 days. The potential of the constructs as 3D in vitro platforms is corroborated by a drug-screening test with doxorubicin, where cells within the model displayed high sensitivity to the drug.