Bacterial cellulose nanofibers reinforced with chitosan/poly-γ-glutamic acid complex for cartilage tissue scaffolding

Tissue engineering offers a promising route to treat cartilage damage caused by trauma or aging due to factors that limit regenerative capacity, such as tissue avascularity, limited nerve fiber distribution, and low cell-to-matrix ratio. It aims to repair hyaline cartilage by introducing chondrocytes or chondrocyte-differentiated stem cells within biocompatible scaffold. This study aimed to develop a composite tissue scaffold with enhanced mechanical strength and the ability to mimic the extracellular matrix of cartilage tissue by forming chitosan and γ-polyglutamic acid (γ-PGA) polyelectrolyte complexes (PECs) in shredded bacterial cellulose (BC). PECs at C:P molar ratios of 30:70, 50:50, and 70:30 were combined with BC at 0.25% and 0.5% w/v. FTIR confirmed characteristic peaks of BC, chitosan, and γ-PGA in the scaffolds. Water-holding capacity (WHC) increased significantly in the BCn-50P50 scaffolds. BC incorporation modulated PEC pore size and distribution most prominently in C30P70 and C70P30, while, overall, scaffolds exhibited a predominant pore-size range of 50-300 μm. Mechanical testing showed bidirectional reinforcement: PECs enhanced the elastic modulus of the BC, and, conversely, BC increased the elastic modulus of PECs. In vitro, all composite scaffolds were biocompatible and BC0.5-C50P50 scaffolds exhibited the best chondrogenic differentiation at day 7 compared to control (p = 0.0015). To our knowledge, this is the first composite scaffold in which PEC forms within BC nanofibers. The composites improved mechanical performance and WHC, expand surface area for cell adhesion, and support chondrogenic differentiation of mesenchymal stem cells.