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NCF/GO hybrid nanofillers with excellent UV-shielding properties were prepared by using TEMPO-oxidized nanocellulose fibrils (NCF) and graphene oxide (GO) as raw materials; different mass ratios of NCF to GO (2: 1, 4: 1, 8: 1, and 16: 1) were used. The NCF and GO were then combined and used as a hybrid filler to study the synergistic effects on polyvinyl alcohol (PVA) nanocomposites. With 5% hybrid nanofiller, the UV-shielding performance of the PVA/NCF/GO composite film was higher than 90%. The tensile strength and Young's modulus of the PVA/CG-2 composite film increased by 74.5% and 278.0%, respectively, and the water absorption decreased by 59%. Moreover, the thermal stabilities of the nanocomposites also improved. This synergistic effect improved the performance of the hybrid nanofiller by avoiding the agglomeration of nanofillers in the polymer matrix and improving the homogeneity of the dispersion. The synergistic effect between the fillers provides a new idea for the preparation of novel multifunctional nanocomposites., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Bacterial cellulose (BC) is a high-purity nanometer cellulose secreted by some bacteria. Compared with plant cellulose, it possesses an array of unique properties, including high crystallinity, high water content, good bio-compatibility, high mechanical strength and an ultra-fine fiber network. BC is prosperous as a new type of biomedical material, which has medical applications such as wound dressing, artificial skin, artificial blood vessels and tissue engineering scaffolds. There are, however, some problems to be solved on the large-scale application of BC, such as the high cost, low yield, and poor mechanical stability and so on.

• Emulsions stabilized by Tempo-oxidized bacterial cellulose present viscoelasticity. • Microrheology results agree well with that from macrorheology. • Rheological features of Pickering emulsions associate closely with physical stability. • Rheological data of Pickering emulsions are useful to predict physical stability. The present study assesses the rheological behaviors of TEMPO-oxidized bacterial cellulose (TOBCs) with diverse oxidation degrees to explore the potential relationship between the rheology and stability of the emulsions. The TOBCs with different oxidation degrees were prepared at the NaClO dosages of 2, 6, and 10 mmol/g, designated 2-TOBC, 6-TOBC, and 10-TOBC, respectively. The small amplitude dynamic rheology and diffusing wave spectroscopy results showed that 2-TOBC emulsion had higher storage modulus G' and loss modulus G" with lower tan δ than 6-TOBC emulsion and possessed the lowest solid-liquid balance among all of the TOBC Pickering emulsions, indicating the highest emulsion stability of 2-TOBC emulsion. Positive correlations existed between the viscoelasticity and stability of the TOBCs Pickering emulsions, with the coefficients of correlation over than 0.6. These results should improve understanding of the relationships between emulsions' stability and rheological characteristics, and lead to a potential application of TEMPO-oxidized bacterial cellulose as an emulsion stabilizer. [ABSTRACT FROM AUTHOR]

In order to seek a safe, biodegradable, and sustainable solid stabilizer for food, topical and pharmaceutical emulsions, individualized cellulose nanofibers were prepared by oxidizing bacterial cellulose (BC) in a Tempo-mediated system; their ability to stabilize oil/water interface was investigated. Significant amounts of C6 carboxylate groups were selectively formed on each cellulose microfibril surface, so that the hydrophilicity was strengthened, leading to lower contact angles. Meanwhile, both the length and width of fibrils were decreased significantly, by partial cleavage of numerous numbers of inter- and intra-fibrillar hydrogen bonds. Tempo-oxidized BC (TOBC) was more effective than BC in stabilizing oil-water interface, attributing to the much smaller size. Fibril dosage and oxidation degree exerted a great influence on the stability and particle size distribution of emulsion samples. When the fibril dosage was 0.7 wt.%, the sample was so stable that it did not experience creaming and coalescence over 8 months. The 2-TOBC coated droplets showed the greatest stability, although both the zeta potential and the electric repulsion were the largest for the 10-TOBC analogue, which was manipulated by the wettability of fibrils. In addition, the stability of samples was analyzed from the viewpoint of particle size distribution. Consequently, fibril size and wettability are two counterbalanced factors influencing the stability of TOBC-stabilized emulsions; a combination of suitable wettability and size imparts TOBC-stabilized emulsion high stability. As a kind of biomass-based particle stabilizer, TOBC showed great potential applications in food, topical and pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Composites of chitosan chloride and bacterial cellulose were successfully prepared by in situ method. Composites of bacterial cellulose/chitosan and pristine bacterial cellulose were investigated by means of scanning electron microscope, atomic force microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and bacteriostatic test. The crystallization of bacterial cellulose was interfered and weakened by the chitosan chloride included in the growth media, resulting in lower crystallinity index and thermal stability. And interaction between two polymers is verified by the thermal gravimetric analysis. The ultrafine nanofibril network structure of bacterial cellulose was retained by the composites, while the diameters were larger and the aperture inside were smaller than those of pristine bacterial cellulose, as shown through scanning electron microscope and atomic force microscope figures. The antimicrobial effects were enhanced by the increasing concentration of chitosan in composites. All the characteristics of the composites provide evidence for the miscibility of chitosan and cellulose. Their biocompatibility is proved through our published data. It is strongly indicated that bacterial cellulose–chitosan nanocomposites have great potential in tissue engineering or pharmaceutical applications in the near future. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, spherical Fe3O4/bacterial cellulose (BC) nanocomposites as adsorbents for heavy metal ions were biosynthesized from Gluconacetobacter xylinum by agitation fermentation. A pH controlling embedding method as a new approach was applied to biosynthesize spherical Fe3O4/BC nanocomposites. Scanning electron microscopy (SEM) images indicated that the Fe3O4 nanoparticles were enwrapped homogeneously in the spherical BC. The spherical Fe3O4/BC nanocomposites with 33wt% ferrous loading had 41emu/g of the saturated magnetization (σ s) and 27Oe of the related coercivity. The adsorption and elution capacities of the spheres for Pb2+, Mn2+, and Cr3+ were evaluated. The results indicated that the spherical Fe3O4/BC nanocomposites had high adsorption capacities and were recyclable after the elution of heavy metal ions. Compared with conventional preparation procedure for cellulose spheres, spherical Fe3O4/BC nanocomposites can be readily prepared without sophisticated steps and have high adsorption and elution capacities. [Copyright &y& Elsevier]