Fabrication of bio-inspired hydrophobic self-assembled electrospun nanofiber based hierarchical structures

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.In this letter, we present a facile approach to fabricate hydrophobic surfaces based on electrostatic field assisted self-assembly of fibers onto conductive micropillars. Hydrophobic patterns fabricated in this work are inspired by an underwater fern Salvinia molesta. Hydrophilic cellulose acetate nanofibers were electrospun on a conducting micro-patterned surface to create a hierarchical structure. The water contact angle increased from just below 70° (hydrophilic) on the micro-patterned structures to ∼140° (hydrophobic) for the hierarchical structures. Introduced hydrophobicity is due to the pinning of the water droplet to suspended hydrophilic nanofibers and a reduced solid-water interface.This work is supported by DST-UKIERI (IND/CONT/E/14-15/370 & DST/INT/UK/P-92/14) project. MK acknowledges assistance with the use of FESEM facility at the University of Exeter. Authors acknowledge IIT Hyderabad for providing research facilities required for carrying out experiment

Orientation of cellulose nanocrystals in electrospun polymer fibres (dataset)

Dataset supporting the open access article.Polystyrene and poly(vinyl alcohol) nanofibres containing cellulose nanocrystals (CNCs) were successfully produced by electrospinning. Knowledge of the local orientation of CNCs in electrospun fibres is critical to understand and exploit their mechanical properties. The orientation of CNCs in these electrospun fibres was investigated using transmission electron microscopy (TEM) and Raman spectroscopy. A Raman band located at ~1095 cm−1, associated with the C–O ring stretching of the cellulose backbone, was used to quantify the orientation of the CNCs within the fibres. Raman spectra were fitted using a theoretical model to characterize the extent of orientation. From these data, it is observed that the CNCs have little orientation along the direction parallel to the axis of the fibres. Evidences for both oriented and non-oriented regions of CNCs in the fibres are presented from TEM images of nanofibres. These results contradict previously published work in this area and micromechanical modelling calculations suggest a uniform orientation of CNCs in electrospun polymer fibres. It is demonstrated that this explains why the mechanical properties of electrospun fibre mats containing CNCs are not always the same as that would be expected for a fully oriented system

Deformation mechanisms in ionic liquid spun cellulose fibers

This is the final version of the article. Available from the publisher via the DOI in this record.The molecular deformation and crystal orientation of a range of next generation regenerated cellulose fibers, produced from an ionic liquid solvent spinning system, are correlated with macroscopic fiber properties. Fibers are drawn at the spinning stage to increase both molecular and crystal orientation in order to achieve a high tensile strength and Young’s modulus for potential use in engineering applications. Raman spectroscopy was utilized to quantify both molecular strain and orientation of fibers deformed in tension. X-ray diffraction was used to characterize crystal orientation of single fibers. These techniques are shown to provide complimentary information on the microstructure of the fibers. A shift in the position of a characteristic Raman band, initially located at ∼1095 cm−1, emanating from the backbone structure of the cellulose polymer chains was followed under tensile deformation. It is shown that the shift rate of this band with respect to strain increases with the draw ratio of the fibers, indicative of an increase in the axial molecular alignment and subsequent deformation of the cellulose chains. A linear relationship between the Raman band shift rate and the modulus was established, indicating that the fibers possess a series aggregate structure of aligned crystalline and amorphous domains. Wide-angle X-ray diffraction data show that crystal orientation increases with an increase in the draw ratio, and a crystalline chain slip model was used to fit the change in orientation with fiber draw ratio. In addition to this a new model is proposed for a series aggregate structure that takes into better account the molecular deformation of the fibers. Using this model a prediction for the crystal modulus of a cellulose-II structure is made (83 GPa) which is shown to be in good agreement with other experimental approaches for its determination.The Engineering and Physical Sciences Research Council (EPSRC) is acknowledged for funding provided under Grant No. EP/L017679/1

Structure of Spherulites in Insulin, β-Lactoglobulin, and Amyloid β

Under denaturing conditions such as low pH and elevated temperatures, proteins in vitro can misfold and aggregate to form long rigid rods called amyloid fibrils; further self-assembly can lead to larger structures termed spherulites. Both of these aggregates resemble amyloid tangles and plaques associated with Alzheimer’s disease in vivo. The ability to form such aggregates in a multitude of different proteins suggests that it is a generic ability in their mechanism to form. Little is known about the structure of these large spherulites ranging from 5 to 100 microns and whether they can reproducibly form in amyloid β (1-40) (Aβ40), a 40-amino acid residue peptide, which is one of the major components of Alzheimer’s amyloid deposits. Here, we show that spherulites can readily form in Aβ40 under certain monomerization and denaturing conditions. Using polarized and nonpolarized Raman spectroscopy, we analyzed the secondary structure of spherulites formed from three different proteins: insulin, β-lactoglobulin (BLG), and Aβ40. Visually, these spherulites have a characteristic “Maltese Cross” structure under crossed polarizers through an optical microscope. However, our results indicate that insulin and Aβ40 spherulites have similar core structures consisting mostly of random coils with radiating fibrils, whereas BLG mostly contains β-sheets and fibrils that are likely to be spiraling from the core to the edge

Stress transfer quantification in gelatin-matrix natural composites with tunable optical properties

© 2015 American Chemical Society.This work reports on the preparation and characterization of natural composite materials prepared from bacterial cellulose (BC) incorporated into a gelatin matrix. Composite morphology was studied using scanning electron microscopy and 2D Raman imaging revealing an inhomogeneous dispersion of BC within the gelatin matrix. The composite materials showed controllable degrees of transparency to visible light and opacity to UV light depending on BC weight fraction. By adding a 10 wt % fraction of BC in gelatin, visible (= 550 nm) and UV (= 350 nm) transmittances were found to decrease by ∼35 and 40%, respectively. Additionally, stress transfer occurring between the gelatin and BC fibrils was quantified using Raman spectroscopy. This is the first report for a gelatin-matrix composite containing cellulose. As a function of strain, two distinct domains, both showing linear relationships, were observed for which an average initial shift rate with respect to strain of -0.63 ± 0.2 cm-1%-1 was observed, followed by an average shift rate of -0.25 ± 0.03 cm-1%-1. The average initial Raman band shift rate value corresponds to an average effective Youngs modulus of 39 ± 13 GPa and 73 ± 25 GPa, respectively, for either a 2D and 3D network of BC fibrils embedded in the gelatin matrix. As a function of stress, a linear relationship was observed with a Raman band shift rate of -27 ± 3 cm-1GPa-1. The potential use of these composite materials as a UV blocking food coating is discussed

Optimization of admixture and three-layer particleboard made from oil palm empty fruit bunch and rubberwood clones

Empty fruit bunch (EFB) is a biomass that is widely available and has the potential to be used as industrial raw material especially in wood-based industries. This study focuses on producing a particleboard by incorporating EFB with two different rubberwood clones: Prang Besar (PB) 260 and RRIM 2002, respectively. PB 260 is a commercially planted clone and wood from matured (>25 year-old) trees are used by wood-based panel manufacturers. RRIM 2002 is a new clone planted at the Malaysian Rubber Board (MRB) research trial plots and consists of only 4-year-old trees. Two types of particleboards (admixture and three-layer) with different ratios were produced. The Japanese Industrial Standard (JIS-5908 2003 particleboard) was used to evaluate mechanical and dimensional stability properties of the particleboards. From the study, it was found that admixture particleboards showed superior properties compared to three-layer particleboards. Layering EFB and rubberwood significantly decreased board performance for all properties (except internal bonding). The optimum ratios of EFB and both rubberwood clones are found to be 1:1 (50% EFB: 50% rubberwood). Meanwhile, increasing the rubberwood clones ratio to 70% lowered board performance especially for EFB (30%):RRIM 2002 clone (70%) boards which showed the lowest values for all properties for both admixture and three-layer board

Primary peritoneal and ovarian cancers: an epidemiological comparative analysis

We performed case–control analyses using data from the North Carolina Ovarian Cancer Study to determine risk factors that distinguish primary peritoneal cancer (PPC) from epithelial ovarian cancer (EOC). Our risk factor analyses were restricted to invasive serous cancers including 495 EOC cases, 62 PPC cases and 1,086 control women. Logistic regression analyses were used to calculate adjusted odds ratios and 95% confidence intervals for risk factor associations. Although many case–control associations for the invasive serous PPC cases were similar to those of the invasive serous EOC cases, some differences were observed including a twofold increase in risk of invasive serous PPC in women who were ≥35 years at last pregnancy, whereas a decreased risk was observed for invasive serous EOC risk. We could not confirm a previous report of an association between tubal ligation and PPC, a factor consistently associated with a decreased risk of EOC. The difference in the risk factor associations between invasive serous PPC and EOC cancers suggests divergent molecular development of peritoneal and ovarian cancers. A larger study to determine risk factors for invasive serous PPC is warranted

Effect of hot calendering on physical properties and water vapor transfer resistance of bacterial cellulose films

This work investigates the effect of hot calendering on bacterial cellulose (BC) films properties, aiming the achievement of good transparency and barrier property. A comparison was made using vegetal cellulose (VC) films on a similar basis weight of around 40 g.m-2. The optical-structural, mechanical and barrier property of BC films were studied and compared with those of highly beaten VC films. The Youngs moduli and tensile index of the BC films are much higher than those obtained for VC (14.5 16.2 GPa vs 10.8 8.7 GPa and 146.7 64.8 N.m.g-1 vs 82.8 40.5 N.m.g-1), respectively. Calendering increased significantly the transparency of BC films from 53.0 % to 73.0 %. The effect of BC ozonation was also studied. Oxidation with ozone somewhat enhanced the brightness and transparency of the BC films, but at the expenses of slightly lower mechanical properties. BC films exhibited a low water vapor transfer rate, when compared to VC films and this property decreased by around 70 % following calendering, for all films tested. These results show that calendering could be used as a process to obtain films suitable for food packaging applications, where transparency, good mechanical performance and barrier properties are important. The BC films obtained herein are valuable products that could be a good alternative to the highly used plastics in this industry.The authors thank FCT (Fundação para a Ciência e Tecnologia) and FEDER (Fundo Europeu de Desenvolvimento Regional) for the financial support of the project FCT PTDC/AGR-FOR/3090/2012— FCOMP-01-0124-FEDER-027948 and the awarding of a research grant for Vera Costa