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Cellulose micro/nanomaterials (CMNM), comprising cellulose microfibrils (CMF), nanofibrils (CNF), and nanocrystals (CNC), are being recognized as promising bio-nanomaterials due to their natural and renewable source, attractive properties, and potential for applications with industrial and economical value. Thus, it is crucial to investigate their potential toxicity before starting their production at a larger scale. The present study aimed at evaluating the cell internalization and in vitro cytotoxicity and genotoxicity of CMNM as compared to two multi-walled carbon nanotubes (MWCNT), NM-401 and NM-402, in A549 cells. The exposure to all studied NM, with the exception of CNC, resulted in evident cellular uptake, as analyzed by transmission electron microscopy. However, none of the CMNM induced cytotoxic effects, in contrast to the cytotoxicity observed for the MWCNT. Furthermore, no genotoxicity was observed for CNF, CNC, and NM-402 (cytokinesis-block micronucleus assay), while CMF and NM-401 were able to significantly raise micronucleus frequency. Only NM-402 was able to induce ROS formation, although it did not induce micronuclei. Thus, it is unlikely that the observed CMF and NM-401 genotoxicity is mediated by oxidative DNA damage. More studies targeting other genotoxicity endpoints and cellular and molecular events are underway to allow for a more comprehensive safety assessment of these nanocelluloses.

The colloidal suspensions of aqueous cellulose nanocrystals (CNCs) are known to form liquid crystalline (LC) systems above certain critical concentrations. From an isotropic phase, tactoid formation, growth, and sedimentation have been determined as the genesis of a high‐density cholesteric phase, which, after drying, originates solid iridescent films. Herein, the coexistence of a liquid crystal upper phase and an isotropic bottom phase in CNC aqueous suspensions at the isotropic–nematic phase separation is reported. Furthermore, isotropic spindle‐like domains are observed in the low‐density LC phase and high‐density LC phases are also prepared. The CNCs isolated from the low‐ and high‐density LC phases are found to have similar average lengths, diameters, and surface charges. The existence of an LC low‐density phase is explained by the presence of air dissolved in the water present within the CNCs. The air dissolves out when the water solidifies into ice and remains within the CNCs. The self‐adjustment of the cellulose chain conformation enables the entrapment of air within the CNCs and CNC buoyancy in aqueous suspensions.

This work describes the synthesis and characterization of a new liquid-crystalline compounds based on isoxazoles. Classical synthetic methodologies were employed in the preparation of this compounds, and the [3+2] 1,3-dipolar cycloaddition was the key step to prepare isoxazolines as precursors to isoxazoles. The structural and thermal characterization was performed using 1 H and 13 C NMR techniques, polarized-light optical microscopy and differential scanning calorimetry. Compounds 7a-e displayed the SmA mesophase. Soft crystal phase (CrE) was observed for compounds 7a and 7b containing chlorine and bromine atoms. For 7e containing a nitro group crystal phases below SmA mesophase were also observed.

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