Oxidative stress actuated by cellulose nanocrystals and nanofibrils in aquatic organisms of different trophic levels

Abstract

Nanocellulose is a functional material derived from natural carbon-based polymers. These nanomaterials are biodegradable and renewable in nature and hence are seen as environmentally-friendly materials in many applications. The use of such innovative materials is accelerating and inescapable there is a need to test these presumed environmentally-friendly materials with regard to their ecotoxicity. Here, the acute toxicity and the oxidative stress of nanocelluloses as induced to three aquatic organisms of different trophic levels, namely Scenedesmus obliquus, Daphnia magna, and Danio rerio, were studied in relation to the composition and morphology of the celluloses. Wood-based cellulose nanocrystals (CNCs), cotton-based CNCs, and cotton-based cellulose nanofibrils were selected as model compounds. The results clearly demonstrated a lack of impact of the different nanocellulose materials on apical endpoints like growth inhibition and mortality after short-term exposure. The nanocellulose materials did activate oxidative stress as evoked by reactive oxygen species in the three aquatic organisms. Key factors ascertained to induce the oxidative stress were the composition and morphology. The nanocellulose induced oxidative stress was observed for all the species at concentrations higher than 0.01 mg/L. This finding suggests a more general revelation of oxidative stress being a characteristic mechanism for nanocellulose toxicity to aquatic organisms.