Engineering sustainable and bioactive 3D-printed cellulose nanofiber scaffolds from kraft pulps with varying lignin levels

Growing interest in cellulose nanofibers (CNFs) for wound-care applications has increased the need for sustainable production routes to deliver high-performance biomaterials. Here, CNFs were produced from bleached and unbleached kraft pulps with different lignin contents and formulated as inks for extrusion-based 3D printing. The influence of pulp composition on TEMPO-mediated oxidation, nanofibrillation, rheological behavior, scaffold architecture, Zn2+ functionalization, and biological performance was systematically evaluated. Residual lignin reduced carboxylation and fibrillation efficiency, resulting in larger fibrillar structures and lower rheological recovery. Nevertheless, both CNF suspensions enabled the fabrication of highly porous (>90%) scaffolds with tunable architectures and comparable mechanical properties. Fibroblast studies confirmed cytocompatibility and revealed sustained cell proliferation, while macrophage cultures showed an early pro-inflammatory response characterized by TNF-α and IL-6 secretion. Zn2+ functionalization generated a burst-release profile during the first hour without affecting scaffold mechanics. Although Zn2+ incorporation markedly reduced fibroblast adhesion, cell viability remained above the cytocompatibility threshold. In addition, Zn2+-loaded scaffolds produced a moderate reduction in bacterial viability and biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa. Despite their different lignin contents, both pulps yielded scaffolds with comparable Zn2+ loading, release behavior, and overall biological performance. These results show that less-refined lignin-containing pulps can be used to produce printable CNFs and functional wound-dressing scaffolds, supporting the use of more sustainable cellulose sources without compromising scaffold performance.