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.