Cellulose nanofibrils as scaffolds for tissue engineering

The purpose of tissue engineering is to regenerate damaged tissue by interplay between stem cells, nutrients and signal molecules, and an artificially created scaffold. The potential of using wood-derived cellulose nanofibril (CNF) hydrogels and cryogelated CNF structures to create the scaffold is studied. In tissue engineering, the micro-environment in the extracellular matrix (ECM) is mimicked. Several factors are important for a successful result. The scaffold must not induce cytotoxicity, the hydrogel or porous structure must be cell friendly and allow for cell growth and vascularization, the stiffness of the scaffold should be similar to the tissue to be regenerated, the surface chemistry should promote cell adhesion, migration and proliferation and finally, the scaffold should gradually degrade when new tissue is formed. How these factors can be complied with is the focus of our research. Control of CNF hydrogel stiffness using either covalent linking or ionic interactions will be presented showing results from rheological assessments. The effect of using two different surface chemistries, TEMPO oxidized CNF (TO-CNF) and carboxymethylated CNF (CM-CNF), on mouse fibroblast cells have been studied in vitro. The samples have been characterized with respect to content of functional groups of CNFs, CNF morphologies and rheological properties of the hydrogels. Independently of the chemical treatments, indirect cytotoxic assessment shows no toxicity of the hydrogels. Response of mouse fibroblasts seeded on the surface or sandwiched in the hydrogels in terms of cytotoxicity, cell attachment, proliferation, morphology and migration have been studied. Results show that the physicochemical environment of the CM-CNF hydrogel maintains cell viability, proliferation and migration but adversely affect cell morphology and spreading. This adverse effect on cell morphology is thought to be a result of the surface chemistry. In contrast, the TO-CNF hydrogel is found to maintain cell spreading and characteristic morphology of fibroblast.