Genotoxic and inflammatory effects of nanofibrillated cellulose in murine lungs.

Nanofibrillated cellulose (NFC) is a sustainable and renewable nanomaterial, with diverse potential applications in the paper and medical industries. As NFC consists of long fibres of high aspect ratio, we examined here whether TEMPO-(2,2,6,6-tetramethyl-piperidin-1-oxyl) oxidised NFC (length 300-1000nm, thickness 10-25nm), administrated by a single pharyngeal aspiration, could be genotoxic to mice, locally in the lungs or systemically in the bone marrow. Female C57Bl/6 mice were treated with four different doses of NFC (10, 40, 80 and 200 µg/mouse), and samples were collected 24h later. DNA damage was assessed by the comet assay in bronchoalveolar lavage (BAL) and lung cells, and chromosome damage by the bone marrow erythrocyte micronucleus assay. Inflammation was evaluated by BAL cell counts and analysis of cytokines and histopathological alterations in the lungs. A significant induction of DNA damage was observed at the two lower doses of NFC in lung cells, whereas no increase was seen in BAL cells. No effect was detected in the bone marrow micronucleus assay, either. NFC increased the recruitment of inflammatory cells to the lungs, together with a dose-dependent increase in mRNA expression of tumour necrosis factor α, interleukins 1ß and 6, and chemokine (C-X-C motif) ligand 5, although there was no effect on the levels of the respective proteins. The histological analysis showed a dose-related accumulation of NFC in the bronchi, the alveoli and some in the cytoplasm of macrophages. In addition, neutrophilic accumulation in the alveolar lung space was observed with increasing dose. Our findings showed that NFC administered by pharyngeal aspiration caused an acute inflammatory response and DNA damage in the lungs, but no systemic genotoxic effect in the bone marrow. The present experimental design did not, however, allow us to determine whether the responses were transient or could persist for a longer time.

Green synthesis of xylan hemicellulose esters.

The esterification of xylan type hemicelluloses, isolated from birchwood, was carried out firstly in homogeneous conditions using N,N-dimethylformamide (DMF) and lithium chloride (LiCl) in the presence of 4-dimethylaminipyridine (DMAP). The degree of substitution (DS) of xylan acetates ranged between 0.9 and 2.0 as a function of experimental conditions. Due to the problems of toxicity and recycling of DMF, an alternative method of esterification is reported in the second part of this work, performing in the absence of organic solvent and using DMAP or methanesulfonic acid (MSA) as catalysts. Acetylation reaction catalyzed by MSA was developed through an experimental design in order to achieve the highest DS under the mildest conditions. The significant factors and their interactions were identified. The optimization of reaction parameters allowed to obtain a high DS (1.6) and maximal yield (85%). Moreover, the reactivity of propionic and hexanoic anhydrides was evaluated and hydrophobic xylan esters with low degrees of substitution were obtained.