Collagen and chitosan blends for 3D bioprinting: A rheological and printability approach

Collagen and chitosan are widely employed as biomaterials, including for 3D-bioprinting. However, the use of collagen and chitosan (col:chi) blends as bioinks is still scarce. In this work, the rheology of different hydrogel precursors (0.5-1.50% w/v chi: 0.18-0.54% w/v col) was analyzed through frequency and strain sweeps, as well as at different shear rates. Col:chi blends showed a shear-thinning behavior, with viscosity values at low shear rates between 0.35 and 2.80 Pa s. Considering the strain rate determined by the applied flow in a 3D-bioprinter, precursor viscosities during the extrusion were in the interval 0.5-0.8 Pa s. Printability (Pr) was measured comparing images of the printed meshes and the corresponding CAD grid design, using photograph analysis. Col: chi 0.36:1.00 was chosen to print mono-layered scaffolds for tissue engineering (TE) because of its suitable viscosity, printability and polymer ratio content. Hydmgels were obtained through NaHCO3 nebulization and 37 degrees incubation, and NHS/EDC were added to obtain scaffolds with improved mechanical behavior. They were stable after 44 h in PBS with collagenase at physiological level and showed no cytotoxic effect in NIH-3T3 fibroblasts.