Bioactive matrix scaffold of oxidized sacchachitin via green catalyst of siliacat tempo for enhancing bone regeneration

Bone regeneration remains a critical challenge in orthopedic medicine. Extracellular matrix proteins play important roles in bionic mineralization and osteogenesis. Sacchachitin nanofibers (SCNFs) oxidized via TEMPO have shown great potential as biomaterial scaffolds due to the introduction of carboxylic groups that mimic the natural extracellular matrix. However, TEMPO is harmful to the environment, which calls for greener and sustainable alternatives. Therefore, this study explored the green fabrication of oxidized-SCNFs through SiliaCat-TEMPO (STEMPO) as a renewable catalyst with various amount of oxidation agents to evaluate their bone regeneration ability. We developed an optimal STEMPO oxidation process, enabling efficient removal of most STEMPO particles through centrifugation with minimal residue. The oxidation efficiency of recovered STEMPO particles remained comparable to fresh ones. STEMPO-oxidized SCNFs, oxidized at increasing NaClO levels, showed an increase in carboxylate content, from 0.1360 mmol/g to 3.2415 mmol/g. Additionally, STEMPO-oxidized SCNFs exhibited excellent biocompatibility with MC3T3-E1 osteoblastic cells, facilitating calcium precipitation, cell migration, and osteogenic differentiation. Mixed composites of β-tricalcium phosphate (BCP) and STEMPO-oxidized SCNFs with higher oxidation levels further enhanced osteogenic differentiation. In vivo studies using a rat femur defect model showed that SCNFs at the highest oxidation level (ST100SC) significantly promoted bone regeneration to full recovery, achieving a bone volume to total tissue volume (BV/TV) ratio of 75.6 %, compared to 48.3 % in the control. These results demonstrated that STEMPO-oxidized SCNFs with higher oxidation levels can be used as a bioactive matrix scaffold to achieve full recovery of bone regeneration.