Three-dimensional scaffolds (3D) with controlled shape, dual porosity and long-term mechanical and dimensional stability in biofluids are of interest as biotemplates in tissue engineering. Herein, self-standing and lightweight cellulose-based biogenic scaffolds with a spatially structured morphology, macropores and interconnected micropores were fabricated using a combination of direct ink writing 3D printing and freeze-drying techniques. This was achieved by developing a water-based and low-cost bicomponent ink based on commercially available nanofibrillated cellulose (NFC) and carboxymethyl cellulose (CMC). Physical cross-linking through dehydrothermal treatment significantly increased the surface hardness, indentation modulus, compression strength, as well as the dimensional stability of the scaffolds in biofluids, in comparison to untreated materials. However, no differences in the spectra of solid state nuclear magnetic resonance or infrared were observed for dehydrothermal treated samples, suggesting that the increase of mechanical properties and dimensional stability is based on the physical cross-linking of functional groups both at the interface between NFC and CMC. The supramolecular structure of the polymers was well-preserved as disclosed by X-ray diffraction measurements. The cross-linked scaffolds showed high proliferation, viability, and attachment of human bone tissue derived osteoblast cells (hFOB). The simple and straightforward avenue proposed here for the design of cellulose-based fibrous inks and dual porous scaffolds from the commercially available materials and without the need of any additional cross-linkers should pave the way for the development of implantable, degradable scaffolds and cell-laden biomaterials for bone tissue regeneration and 3D bioprinting applications.
Keywords: 3D printing; carboxymethyl cellulose; cell testing; dual porosity; freeze-drying; nanofibrillated cellulose; scaffolds; solid-state NMR.