Integration of cellulose nanofibers in the formulation of PLA/HAp filaments: an alternative to their application as ECM

The need for advanced biomimetic biomaterials is critical in tissue engineering due to the rising demand for bone grafts and the limitations of conventional methods. In this context, the combination of bio-based nanocellulose matrix and hydroxyapatite (HAp) has garnered significant interest because of the complementary advantages these materials offer [1]. Nanoellulose provides mechanical strength, flexibility, and biodegradability, while HAp contributes its bioactivity, biocompatibility, and osteoinductivity [2]. This study proposes a dual role of cellulose nanofibers (CNF) as a mechanical nano-reinforcement within the solid matrix and as a biomimetic supporter within a hydrogel phase for bone tissue engineering. CNF were obtained through an integral biorefinery process of agro-industrial by-products, aligning the fabrication with circular economy principles and sustainability goals. To produce advanced filaments ensuring optimal integration, a colloidal route was developed to incorporate the CNF and HAp into a PLA matrix. This formulation does not compromise the fused filament fabrication (FFF) process, instead, it significantly enhances the microstructural properties by creating a tailored porosity that increases the specific surface area. The 3D-printed scaffolds structural integrity and functional behavior were assessed. Degradation assays revealed that the presence of CNF facilitates a sustained and enhanced release of calcium ions, a critical factor for triggering osteogenic signaling pathways. Additionally, CNF exhibited a buffering capacity that mitigates the autocatalytic acidification typical of PLA degradation, thereby maintaining a physiological pH environment that optimized the conditions for bone ingrowth. Biological validation through cell viability studies confirmed their potential as safe and bioactive grafts. The synergy between HAp and the waste-derived CNF provides a sustainable, high-performance alternative for bone tissue engineering.