Eco-friendly nanocellulose-reinforced polysaccharide gels: Role of composition in structural, swelling and mechanical performance

Various compositions of nanocellulose-reinforced chitosan and alginate cryo- and hydrogels were prepared using environmentally friendly methods. Their structure, swelling behavior, and compression modulus were systematically investigated. The total polymer concentration varied between 1 and 4 g/100 mL, and chitosan and alginate gels were further modified by incorporating either 0 or 5% bacterial cellulose or nanofibrillated cellulose. Gels containing 4 g/100 mL of polysaccharide exhibited a high degree of structural order, which progressively decreased with lowering polymer concentration. Increasing the concentration of chitosan and alginate resulted in higher apparent density and lower equilibrium swelling, and significantly enhanced stiffness of the cryogels. A comparable trend was observed for the hydrogels, where a higher polysaccharide content led to an increased compression modulus; however, the modulus of the hydrogels was approximately one-fifth of that measured for the corresponding cryogels. Chitosan-based gels showed a slightly more compact structure than alginate-based ones. Consequently, chitosan cryogels exhibited higher density and modulus, along with lower swelling compared to their alginate counterparts. The addition of 5% nanocellulose notably enhanced both the swelling capacity and modulus of the cryogels, while smaller moduli improvements were observed for the hydrogels. The highest modulus (239 kPa) was obtained for a chitosan/bacterial nanocellulose cryogel.