RESUMO

Composite films of nanofibrillated cellulose (NFC) and chitosan (CS) were prepared by spray deposition method, and the influence of polymers ratio and protonation degree (α) of chitosan was evaluated. Films were characterized using morphological, mechanical, and surface techniques. Higher NFC content increased Young's modulus of film composites and reduced air permeability, while higher CS content increased water contact angle. Variations in the degree of protonation of chitosan from non-protonated (α = 0) to fully protonated (α = 1) in the NFC/CS composite film with a fixed composition allowed to modulate surface, mechanical, and structural properties, such as water contact angle (31.3-109.2°), Young's modulus (1.7-5.3 GPa), elongation at break (3.1-1.2 %), oxygen transmission rate (9.0-5.5 cm3/m2day) and air permeability (2074-426 s). Highly protonated chitosan composite films showed similar contact angles to pure chitosan films, while low protonated chitosan composite films presented contact angles similar to pure NFC films, suggesting a possible coating effect of NFC by CS through electrostatic interactions, evidenced by microscopy and spectroscopy analysis. By mixing both polymers and adjusting composition and protonation degree it was possible to enhance their properties, making pH adjustment a useful tool for NFC/CS composite films formation.

Assuntos

RESUMO

Tobacco stalk is a cellulose-rich material and a sustainable alternative to be applied as a plant-based nanofibrillated cellulose (NFC) source. NFC use has garnered attention in the development of oral pharmaceutical forms, despite concerns about its safety due to the adverse effects of nicotine on health. Therefore, we aimed at establishing the safety of NFC derived from tobacco stalk for its potential use as a novel pharmaceutical excipient, exploring its potential functions for tablet production. We conducted acute and subchronic oral toxicity tests in adult female Wistar rats. Initially, individual animals received sequential doses (175-5,000 mg·kg-1) for 24 hours followed by a careful observation of any toxic effects. Subsequently, 20 rats were divided into four groups for a subchronic assay, evaluating toxicity signs, body weight changes, hematological, biochemical, and histopathological parameters. No deaths or other clinical toxicity signs were observed in either the acute or the subchronic assays. We noticed a significant reduction in body weight gain (p < 0.05) after 14 days. We found statistical differences for hematological and biochemical parameters, unrelated to dosage. There were no observed toxic effects, and tobacco stalk ingestion did not adversely affect organ morphology in the histopathological evaluation. The oral administration of NFC at 5,000 mg·kg-1 per day for 28 days was well-tolerated by treated rats, with no reported deaths. In conclusion, NFC derived from tobacco stalk has shown to be a sustainable and safe alternative for use as an excipient at experimental doses, demonstrating compatibility with its proposed applications.

Assuntos

RESUMO

Nanocellulose is a well-known stabilizer for several colloidal dispersions, including emulsions and solid nanoparticles, replacing surfactants, polymers, and other additives, and therefore providing more minimalistic and eco-friendly formulations. However, could this ability be extended to stabilize oil droplets and inorganic nanoparticles simultaneously in the same colloidal system? This work aimed to answer this question. We evaluated both cationic and anionic nanofibrillated celluloses to stabilize both titanium dioxide nanoparticles and oil droplets. The resulting suspensions held their macroscopic stability for up to 2 months, regardless of pH or surface charge. Cryo-TEM images revealed a complex network formation involving nanofibers and TiO2 nanoparticles, which agrees with the high viscosity values and gel-like behavior found in rheology measurements. We propose that the formation of this network is responsible for the simultaneous stabilization of oil droplets and TiO2 nanoparticles, and that this may be used as a formulation tool for other complex systems.

Assuntos

RESUMO

Specific kinds of enzymes have been used as an eco-friendly pre-treatment for mechanical extraction of cellulose nanofibrils (CNFs) from vegetal pulps. Another well-established pre-treatment is the 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-mediated oxidation, which has gained considerable attention. Pre-treatments assist in fiber swelling, facilitating mechanical fibrillation, and reducing energy consumption; however, some of these methods are extremely expensive. This work aimed to evaluate the influence of enzymatic pre-treatment with endoglucanase on the energy consumption during mechanical fibrillation of cellulose pulps. Bleached pulps from Eucalyptus sp. and Pinus sp. were pre-treated with endoglucanase enzyme compared to TEMPO-meditated oxidation. Average diameters of CNFs pre-treated with enzymes were close to that found for TEMPO-oxidized nanofibrils (TOCNFs). Results showed that enzymatic pre-treatment did not significantly modify the pulp chemical and morphological characteristics with efficient stabilization of the CNFs suspension at higher supernatant turbidity. Energy consumption of pulps treated with endoglucanase enzymes was lower than that shown by pulps treated with TEMPO, reaching up to 58% of energy savings. The enzyme studied in the pulp treatment showed high efficiency in reducing energy consumption during mechanical fibrillation and production of films with high mechanical quality, being an eco-friendly option for pulp treatment.

Assuntos

RESUMO

HYPOTHESIS: Hydrophobic oleic acid/water interfaces are negatively charged. Hence, the use of cationic nanocelluloses as stabilizers of Pickering emulsions could improve the colloidal stability due to the electrostatic complexation at the oil-water interface. EXPERIMENTS: Two cationic nanofibrillated cellulose (cNFCs) with two degrees of substitution were prepared and used as stabilizers of Pickering emulsions. The adsorption of cNFCs at the oil: water interface was evaluated by interfacial tension, atomic force microscopy, and centrifugation measurements. LUMiSizer and optical microscopy techniques were used to analyze the colloidal stability and oil droplets morphology, respectively. Besides, the rheological behavior of the continuous aqueous phase was determined through flow and stress sweep curves. Finally, the dispersion of cNFCs in a diluted emulsion was visualized by cryogenic transmission electron microscopy (cryo-TEM). FINDINGS: Cationic NFCs were more efficient in partitioning to the oil:water interface compared to their anionic analogous, oCNF. The electrostatic attraction between the positively charged trimethylammonium groups and the negatively charged deprotonated oleic acid reduced the interfacial tension and improved the colloidal stability of O/W Pickering emulsions. cNFCs dispersed in the aqueous phase were found to increase the viscosity, decelerating the oil drops coalescence. Therefore, the stabilization of cNFCs Pickering emulsions had a synergistic effect from the electrostatic complexation at the liquid-liquid interface and network formation in the aqueous phase, as visualized by cryo-TEM.

RESUMO

Cellulose nanofibers (CNF) were isolated from Curauá fibers (Ananas erectifolius L. B. Smith) through a mechanical grinder preceded by mild chemical treatment. Morphology and surface characteristics of the fibers were followed until it reaches the nanoscale as long and flexible nanofibers. In aqueous suspensions, SAXS techniques revealed that such nanofibers present a twisted ribbon structure while rheological measurements demonstrate its high viscosity and a thixotropic behavior. These characteristics suggests the potential application of CNF in biomedical field, which, in turn, stimulates the toxicological studies of such materials. The obtained materials do not show any sign of cytotoxicity by direct or indirect assays for cell viability and cell morphology using Vero cells. Moreover, during the adhesion test, the cells demonstrated higher affinity to the CNF surface. It can be related to its surface properties and its obtaining conditions, which did not use any hazardous chemicals.

Assuntos