Cellulose esters: Synthesis for further formation of films with magnetite nanoparticles incorporated

This study investigated the homogeneous synthesis of cellulose acetate (CA) and propionate (CP) with varying degrees of substitution (DS) from sisal cellulose in a N, N-dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system. These esters were used to prepare neat (CADSF/CPDSF) and nanocomposite films (CADSFFe/CPDSFFe) from prior synthesized magnetite nanoparticles (NPs, Fe3O4, 5.1 ± 0.5 nm). Among the CA and CP series, the composite CA0.7FFe and the neat CP0.7F films exhibited the highest modulus of elasticity, 2105 MPa and 2768 MPa, respectively, probably a consequence of the continuous fibrous structures present on the surface of these films. Microsphere formation on the film's surface was observed in scanning electron microscopy micrographs. This points to applications in the controlled release of targeted substances. The VSM analysis showed that the cellulosic matrices preserved the superparamagnetic characteristics of the NPs. This study suggested a reduced coupling effect between nanoparticles inside polymeric films due to magnetic saturation at low fields. CA0.7FFe and CA1.3FFe composite films reached a saturation magnetization (MSAT) of 46 emu/g around 7 kOe field. Hosting magnetite nanoparticles in cellulose ester matrices may be an interesting way to develop new functional cellulose-based materials, which have the potential for diverse applications, including microelectromechanical systems and microsensors.

Metallic nanoparticle contamination from environmental atmospheric particulate matter in the last slab of the trophic chain: Nanocrystallography, subcellular localization and toxicity effects

Atmospheric particulate material (PM) from mining and steel industries comprises several metallic contaminants. PM₁₀ samples collected in a Brazilian region with a recognized influence of the steel and iron pelletizing industries were used to investigate metallic nanoparticle incorporation into human fibroblast cells (MRC-5). MRC-5 cells were exposed to 0 (control, ultrapure water), 2.5, 5, 10, 20 and 40 μg PM₁₀ mL^-1, for 24 h. Cytotoxic and genotoxic dose-response effects were observed on lysosome and DNA structure, and concentrations high as 20 and 40 μg PM₁₀ mL^-1 induced elevated cell death. Ultrastructure analyses showed aluminosilicate, iron, and the emerging metallic contaminants titanium, bismuth, and cerium nanoparticles were incorporated into lung cells, in which the nanocrystallography analysis indicated the bismuth as Bi₂O₃. All internalized metallic nanoparticles were free and unbound in the cytoplasm and nucleus thereby indicating bioavailability and potential interaction to biological processes and cellular structures. Pearson's correlation analysis showed Fe, Ni, Al, Cr, Pb and Hg as the main cytotoxic elements which are associated with the stainless steel production. The presence of internalized nanoparticles in human lung cells exposed to environmental atmospheric matter highlights the need for a greater effort by regulatory agencies to understand their potential damage and hence the need for future regulation, especially of emerging metallic contaminants.