Composite nano-fibrillated cellulose-alginate hydrogels: Effect of chemical composition on 3D extrusion printing and drug release

In this work, composite hydrogels of nanofibrilated cellulose (CNF) and alginate were prepared through direct addition of alginate in powder to a CNF hydrogel. Alginate was hydrophobically modified with C8 alkyl chains (HMAlg), and the effect of chemical modification on the rheological properties and printability of the resulting composite gels was evaluated. The rheological characterization of the composite hydrogels indicated that the addition of alginate, non-modified and HMAlg, did not influence the zero-shear rate viscosity or the mechanical properties of the pristine CNF hydrogels. Printability tests showed that the incorporation of alginate, especially HMAlg, hindered the manufacture of well-defined 3D polymeric structures through 3D extrusion printing. This effect was much more pronounced with the incorporation of bovine serum albumin (BSA) into the gels, which was ascribed to the presence of interactions between the polymer matrix and the BSA. Finally, experiments of BSA release were run with 3D-printed samples, showing that controlled release could be achieved from CNFs gels.