Problem definition and objectives: In the past two decades, integrating specialized or stem cells with biodegradable three-dimensional scaffolds and a variety of biochemical, physical, and mechanical cues has opened new avenues for reconstructing the structural and functional properties of impaired tissues. These components exhibit their highest efficacy when incorporated into a coordinated system that closely mimics the physiological microenvironment of native tissue. Among the available fabrication technologies, three-dimensional printing particularly direct ink writing (DIW) has gained significant attention due to its precise control over ink rheology, tunable internal architecture, adjustable porosity and pore orientation, and the ability to combine multiple biomaterials simultaneously. This technology enables the fabrication of scaffolds with complex geometries analogous to native tissues, providing a conducive platform for cell adhesion, proliferation, and differentiation. The selection of appropriate bio-ink constituents is therefore a critical aspect of scaffold development. Nanocellulose, a natural and renewable polymer, offers high mechanical strength, robust three-dimensional network formation, excellent biocompatibility, and tunable surface chemistry, making it an attractive candidate for bio-ink formulation. Complementarily, lignin, an abundant aromatic biopolymer, provides antioxidant activity, moderate hydrophobicity, and reinforcing capability, thereby influencing the rheological behavior, printability, and mechanical performance of printed scaffolds. Polyvinyl alcohol (PVA), with its ability to form stable hydrogels, favorable flexibility, and coherent network structure, further enhances the stability, uniformity, and integrity of the composite scaffold. Given the growing demand for biodegradable and renewable biomaterials in scaffold fabrication, the present study investigates the effect of varying lignin content within nanocellulose/PVA-based systems. The objective is to elucidate how lignin concentration influences structural stability, chemical behavior, water absorption capacity, wettability, and ultimately the biodegradability of the resulting scaffolds. This work aims to identify an optimized material composition capable of producing high-performance scaffolds suitable for both clinical and research-based tissue engineering applications.
Methodology: In this study, PVA/nanocellulose/lignin composite scaffolds containing 10%, 20%, and 30% lignin were fabricated via 3D bio-printing. Morphological features were assessed by scanning electron microscopy (SEM), chemical interactions analyzed through Fourier-transform infrared spectroscopy (FTIR), water absorption and long-term hydrophilicity evaluated, and surface wettability measured via contact angle analysis. Biodegradability was monitored in phosphate-buffered saline at 37 °C over three months.

Results: SEM images revealed that low lignin content maintained a uniform and stable PVA/nanocellulose network, while 30% lignin induced phase separation and agglomeration, reducing structural coherence. FTIR spectra indicated improved interfacial interactions through hydrogen bonding and partial coating of nanocellulose by lignin. Water absorption decreased and contact angles increased with higher lignin content, reflecting reduced hydrophilicity and enhanced moisture resistance, largely due to lignin’s hydrophobicity and citric-acid-induced esterification. Biodegradation results demonstrated that lignin’s aromatic structure slowed scaffold degradation. Overall, moderate lignin incorporation enhanced matrix cohesion, controlled water affinity, and preserved structural stability, whereas excessive lignin compromised scaffold integrity.

Conclusion: These findings highlight that optimizing lignin concentration is critical to achieving desirable morphological, physicochemical, and biodegradation properties in PVA/nanocellulose scaffolds, providing a promising approach for tissue engineering applications. Based on the results, the formulation containing 20% lignin exhibited the best balance between structural stability, water absorption, and biodegradability, and could be proposed as a suitable candidate for the development of bio-scaffolds in tissue engineering.