Occupational exposure to emerging cellulose nanomaterials and potential respiratory effects: uncovering exposure-effect relationships using in vitro systems

The application of innovative cellulose nanomaterials (CNMs), particularly, cellulose micro- and nanofibrils (CMF, CNF) and nanocrystals (CNC), in technology and biomedicine has expanded in recent years. However, there is still a lack of reliable indicators to assess workers’ exposure, mainly by inhalation, and the associated health outcomes. This study aimed at identifying genotoxic, oxidative stress, or epigenetic endpoints that could be used as promising effect biomarkers to predict health outcomes from CNMs exposure, exploitable for human biomonitoring. Three well-characterized CNMs were used, at a low concentration range, to expose cell systems representative of the respiratory tract, namely, bronchial epithelial (BEAS-2B) cells or co-cultures of lung (A549) and macrophage-like (THP-1) cells. No induction of chromosomal instability was detected in co-cultures for all types of CNMs analysed through the cytokinesis-block micronucleus assay. Likewise, neither significant toxic effects nor oxidative stress was found. Interestingly, preliminary data showed differentially expressed microRNAs in BEAS-2B cells after exposure to CNC, but not to CMF or CNF, compared to untreated cells. Moreover, a profile of microRNAs associated with CNC exposure was identified. Overall, no major concern regarding CNMs genotoxicity and oxidative stress was raised. Epigenetic effects were uncovered for CNC and the identified miRNA profile has potential to be used as an effect biomarker for occupational biomonitoring. However, further investigation with longer exposures and validation of that profile using in vivo models must be conducted, to prove its value to assess early effects from CNMs exposure.Portuguese Foundation for Science and Technology (FCT/MCTES),through national funds(PIDDAC)(PTDC/SAU-PUB/32587/2017 and PTDC/SAU-PUB/29481/2017); ToxOmics - Centro de Investigação em Toxicogenómica e Saúde Humana - UIDP/00009/2020N/