Producing ultrapure wood cellulose nanofibrils and evaluating the cytotoxicity using human skin cells

• Ultrapure wood cellulose nanofibrils (CNF) have been produced with a final endotoxin level of 45 endotoxin units/g cellulose.
• CNF dispersion (50 μg/ml) did not affect the cytotoxicity or metabolic activity of fibroblasts and keratinocytes.
• Aerogels made of CNF induced a reduction of metabolic activity by the fibroblasts and keratinocytes, but no significant cell death.
• Cytokine profiling revealed that the keratinocytes and fibroblasts did not induce cytokines upon direct exposure to the CNF materials.
• Due to the nano dimension of the CNFs, the aerogels had a high moisture-holding capacity (∼7500%).

Wood cellulose nanofibrils (CNF) have been suggested as a potential wound healing material, but its utilization is limited by FDA requirements regarding endotoxin levels. In this study a method using sodium hydroxide followed by TEMPO mediated oxidation was developed to produce ultrapure cellulose nanofibrils, with an endotoxin level of 45 endotoxin units/g (EU/g) cellulose. Scanning transmission electron microscopy (S(T)EM) revealed a highly nanofibrillated structure (lateral width of 3.7 ± 1.3 nm).Assessment of cytotoxicity and metabolic activity on Normal Human Dermal Fibroblasts and Human Epidermal Keratinocytes was done. CNF-dispersion of 50 μg/ml did not affect the cells. CNF-aerogels induced a reduction of metabolic activity by the fibroblasts and keratinocytes, but no significant cell death. Cytokine profiling revealed no induction of the 27 cytokines tested upon exposure to CNF. The moisture-holding capacity of aerogels was relatively high (∼7500%), compared to a commercially available wound dressing (∼2500%), indicating that the CNF material is promising as dressing material for management of wounds with a moderate to high amount of exudate.