Diameter Of Nanofibrils Research Articles

Formation of tannic acid-binding ovalbumin amyloid fibril hydrogels: Enhanced antibacterial and antioxidant properties

The protein-induced amyloid fibrils (AFs) are limited in food industry due to their poor antioxidant and antibacterial activities. However, polyphenol shows the potential functional modifications of AFs, and extend their application in food processing. In present study, tannic acid-binding ovalbumin-induced AFs (TA-OAFs) hydrogels were fabricated via different concentrations of TA and ovalbumin amyloid fibrils, and the rheological properties, thermal stability, and morphology of the hydrogels were investigated. Then, the physiochemical, antioxidant, and antibacterial of TA-OAFs hydrogels were further analyzed. The obtained results indicated that the addition of TA could increase the average diameter of nanofibrils with increased β-sheet contents, and showed a TA concentration-dependent tendency. Moreover, TA-OAFs hydrogels also possessed better thermal stability, antioxidant activity, and antibacterial capacity for both Gram-negative and Gram-positive bacteria. The present study might contribute to a better understanding of antimicrobial materials designing of protein-induced amyloid fibrils in the food field with beneficial properties.

Development of a bacterial cellulose-gelatin composite as a suitable scaffold for cardiac tissue engineering.

Cardiac tissue engineering is suggested as a promising approach to overcome problems associated with impaired myocardium. This is the first study to investigate the use of BC and gelatin for cardiomyocyte adhesion and growth. Bacterial cellulose (BC) membranes were produced by Komagataeibacter xylinus and coated or mixed with gelatin to make gelatin-coated BC (BCG) or gelatin-mixed BC (mBCG) scaffolds, respectively. BC based-scaffolds were characterized via SEM, FTIR, XRD, and AFM. Neonatal rat-ventricular cardiomyocytes (nr-vCMCs) were cultured on the scaffolds to check the capability of the composites for cardiomyocyte attachment, growth and expansion. The average nanofibrils diameter in all scaffolds was suitable (~ 30-65nm) for nr-vCMCs culture. Pore diameter (≥ 10µm), surface roughness (~ 182nm), elastic modulus (0.075 ± 0.015MPa) in mBCG were in accordance with cardiomyocyte requirements, so that mBCG could better support attachment of nr-vCMCs with high concentration of gelatin, and appropriate surface roughness. Also, it could better support growth and expansion of nr-vCMCs due to submicron scale of nanofibrils and proper elasticity (~ 0.075MPa). The viability of nr-vCMCs on BC and BCG scaffolds was very low even at day 2 of culture (~ ≤ 40%), but, mBCG could promote a metabolic active state of nr-vCMCs until day 7 (~ ≥ 50%). According to our results, mBCG scaffold was the most suitable composite for cardiomyocyte culture, regarding its physicochemical and cell characteristics. It is suggested that improvement in mBCG stability and cell attachment features may provide a convenient scaffold for cardiac tissue engineering.

P/N/S synergistic flame retardant holocellulose nanofibrils efficiently pretreated from ternary deep eutectic solvents

Cellulose nanofibrils (CNFs) have widely attracted significant attention due to the excellent mechanical performance, biodegradability, and high surface functionality. However, the high flammability of CNFs commonly restricts their wider application. In this study, the intrinsically flame-resistant holocellulose nanofibrils (HCNFs, which is rich in both cellulose and hemicellulose) were obtained from bamboo under pretreatment using a highly efficient ternary deep eutectic solvent (TDES) and subsequential mechanical homogenization. The phytates and sulfate-containing HCNFs (PHCNFs) displayed nanofibril diameter of 3–5 nm and high aspect ratio of (∼500), and the aqueous suspension exhibited colloidal stability and high transmittance. The PHCNF films exhibited excellent fire resistance, mechanical and optical properties. Compared with raw HCNF, the limiting oxygen index (LOI) of PHCNF-120 film was up to 52.5 %, and the total heat release (THR) and peak heat release rate (PHRR) of PHCNF-120 films were significantly reduced by 92.2 % and 82.4 %, respectively. The flame retardant mechanism was attributed to the synergistic effect of P/N/S in both condensed phase and gaseous phases during the burning process. This work provides a novel, efficient strategy for developing eco-friendly flame-resistant and fireproof holocellulose-based nanomaterials.

In situ nanofibrillar composite fiber: A model system for understanding the structural evolution of crosslinked nanofibrils

AbstractIn situ formed nanofibrils, which are formed from the deformation of dispersed phase polymer during the shearing/stretching process, offer exciting opportunities for large scale manufacture of materials with high strength and toughness. However, how the topological structure, especially crosslinking network structure of dispersed phase polymer, affects the structural evolution of nano/microfibrils is remaining unclear. Here, the nanofibrillar morphology of nanofibrillar composite fibers is manipulated via controlling the crosslinking network structure of dispersed phase. By changing the length of crosslinker and mol ratio of crosslinkers, the diameter of nanofibrils can be controlled. The rheological property of the crosslinked microspheres and corresponding morphology of in situ formed nanofibrils confirm that the inhomogeneous crosslinking network shows lower storage modulus and consistency coefficient, leading to higher deformation adaptability of crosslinking network and smaller diameter of the nanofibrils. The distribution of nanofibrils along the axial direction of composite fiber greatly improved the tensile strength and toughness of composite fiber to 74 MPa and 719 MJ/m3, which are 45% and 180% increasement compared with the counterpart pure PMMA fiber. The findings in current study provide a new strategy to control the nanofibrillar morphology by increasing the heterogeneity of crosslinking network structure of the dispersed phase polymer.

Dependency of morphological and optical properties of electropolymerized PAni thin films on different substrate for supercapacitor applications

Morphological and optical properties have been investigated for electrochemically deposited polyaniline (PAni) thin films on various substrates, having different transparent conducting oxides (TCO) layer viz. ITO and FTO. Different substrates have facilate the nucleation formation for the growth of nanostructures and control the length of the diameter of nanofibrils. Diameter of the nano-fibrils can facilate the transfer of ions and electrons and hence it affects the pseudocapacitor nature of thin films. Contact angle measurements of thin films depict that hydrophilic nature of PAni thin films also depend on different substrates. Moreover, morphology dependent electrochemical performances of PAni thin films were investigated using cyclic voltametry. Photoluminescence emission has shown pronounce effect due to the variation of substrate. PAni thin films can be used as supercapacitors by tuning their capacitance by varying substrate used as working electrode.

Study on Morphology, Thermal and Rheological Properties of Polypropylene/Poly(trimethylene terephthalate) Polyblend Fibers

In the present work, a systematic study of the variables affecting the production of polypropylene (PP)/poly(trimethylene terephthalate) (PTT) blend fibers such as the PTT and PP-g-MA compatibleizer ratios and take-up speed in the melt-spinning process was done. Modeling of the melt-spinning process was carried out by using a statistical approach based on response surface methodology (RSM) to achieve a mathematical model. The formation of the fibrillar structures through different steps of fiber formation was confirmed by scanning electron microscopy (SEM). The lowest mean diameter of nano-fibrils was achieved to be 63 nm, for the hot-drawn fibers consisting of 10 wt.% of PTT. The synergetic effect of the presence of PTT dispersed phase on the mechanical properties of PP fibers as a matrix was verified by observing a positive deviation from the blends linear law for the samples with 10 wt.% of PTT. The rheological evaluations suggested the formation of a fibril structure in the blends. The X-ray diffraction spectroscopy and DSC results showed that the presence of PTT significantly influenced the crystallinity of PP. Moreover, results indicated that the average crystal size of the PP matrix phase was affected by the presence of the PTT dispersed phase, which also confirmed its nucleating effect in the blend.

Characterization of Ground Silk Fibroin through Comparison of Nanofibroin and Higher Order Structures.

Silk fibroin, a biodegradable component of silk, is increasingly used for various applications and studied intensively. Recently, a technique for preparing nanofibers without using chemicals has been gaining attention from the environmental impact and safety perspectives. This study focuses on the structure observation of ground silk fibroin (GF) prepared using a grinding method, which is a physical nanofibrillation method. The fabricated nanofiber samples were examined in detail using the X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro Raman spectroscopy, and atomic force microscopy (AFM) techniques. The nanofibrillated structures were observed in both GF and regenerated silk fibroin (RF) samples prepared using the conventional method. As results, AFM images showed that the nanofibril diameter of GF was about 1.64 nm and that of RF was about 0.32 nm. Methanol treatment induced a structural transition from a random coil to a β-sheet for the RF film, but it had no effect on the GF film. Thus, it is suggested that the grinding method provides not only ultrafine silk fibroin nanofibers without using toxic reagents but also resistance to reagents such as methanol.

Identifying Juncus plant as viable source for the production of micro- and nano-cellulose fibers: Application for PVA composite materials development

With the aim of identifying new, renewable and sustainable sources for the production of bio-nano-materials, cellulose microfibers (CMF) and cellulose nanofibrils (CNF) were successfully produced from the widely available Juncus plant. CMF with average microfibers diameter of 3.5 μm were produced by conventional alkaline and bleaching treatments with a yield of around 36 %. CNF with average nanofibrils diameter of 2.5 nm were isolated from CMF by a combination of TEMPO-oxidation and mechanical disintegration processes. The morphology and physico-chemical properties of raw Juncus plant stems, CMF, TEMPO-oxidized CMF (T-CMF) and CNF were evaluated using several characterization techniques. It was found that the applied chemical treatments were effective in producing pure CMF and CNF materials having typical cellulose I structure, high crystallinity and good thermal stability. The as-extracted CNF were utilized to develop CNF-reinforced PVA nanocomposite films, and their transparency, thermal stability and mechanical properties were investigated and compared with the CMF and T-CMF reinforced PVA composite materials. It was found that the PVA nanocomposite material containing 5 wt% CNF exhibited a tensile modulus and strength of 3.3 GPa and 110 MPa, respectively, which are higher than those observed for neat PVA and PVA composites reinforced with 5 wt% CMF or T-CMF (modulus of 1.9 and 3.1 GPa and strength of 52 and 97 MPa, respectively). In contrast to CMF and T-CMF reinforced PVA composites, that displayed a reduced optical transmittance (ca. 57–70 % at 600 nm), the CNF-reinforced PVA nanocomposite material maintained the same transmittance of the neat PVA film (ca. 90 % at 600 nm), suggesting the good dispersion of CNF at the nanometric scale. These newly developed CNF could be considered as a potential nanofiller candidate for the preparation of PVA-based nanocomposite materials of high transparency and good mechanical properties.

Production of cellulose nanofibrils from alfa fibers and its nanoreinforcement potential in polymer nanocomposites

Alfa fibers (Stipa Tenacissima) were effectively utilized in this study as a promising cellulose source for isolation of carboxy-functionalized cellulose nanofibrils (CNFs) using multiple treatments. Pure cellulose microfibers (CMFs) were firstly extracted by alkali and bleaching treatments. CNFs with an average nanofibrils diameter ranging from 1.4 to 4.6 nm and a crystallinity of 89% were isolated from CMFs by a combination of TEMPO-oxidation and mechanical disintegration processes. The morphology and physico-chemical properties of cellulosic materials were evaluated at different stages of treatments using several characterization techniques. Various CNF loadings (5–15 wt%) were incorporated into PVA polymer to evaluate the nanoreinforcement ability of CNFs and to produce CNF-filled PVA nanocomposite materials. The tensile and optical transmittance properties, as well as the morphological and thermal properties of the as-produced CNF-filled PVA nanocomposite films were investigated. It was found that the tensile modulus and strength of nanocomposites were gradually increased with increasing of CNF loadings, with a maximum increase of 90% and 74% was observed for a PVA nanocomposite containing 15 wt% CNFs, respectively. The optical transmittance was reduced from 91% (at 650 nm) for neat PVA polymer to 88%, 82% and 76% for PVA nanocomposites containing 5, 10 and 15 wt% CNFs, respectively. It was also found that the glass transition temperature was gradually increased from 76 °C for neat PVA to 89 °C for PVA nanocomposite containing 15 wt%. This study demonstrates the importance of Alfa fibers as annual renewable lignocellulosic material to produce CNFs with good morphology and excellent properties. These newly developed carboxy-functionalized CNFs could be considered as a potential nanofiller candidate for the preparation of nanocomposite materials of high transparency and good mechanical properties.

Preparation and characterization of electrospun composite nanofibers from poly(vinyl alcohol) /lignocellulose nanofibrils with different chemical compositions

Lignocellulose nanofibrils (LCNFs) were prepared using Liriodendron tulipifera L. wood flour. Electrospun nanofibers were fabricated by mixing the LCNFs with poly(vinyl alcohol) (PVOH). The lignin and hemicellulose contents of the wood flour were controlled with an alkaline-peroxide treatment at a pH of 11.5 using various hydrogen peroxide concentrations. The morphological characteristics, mean diameter, and filtration time of the LCNFs subjected to wet disk milling (WDM) and high-pressure homogenization were determined. Furthermore, the spinning suspension viscosity was measured with various LCNF concentrations and PVOH/LCNF addition ratios. After the alkaline-peroxide treatment, the lignin and hemicellulose contents decreased with an increasing hydrogen peroxide concentration and reaction time. As the lignin content decreased, the nanofibril diameter decreased and the filtration time increased. The diameter decreased further after the homogenization treatment following WDM. The viscosity of the mixed solution increased with an increasing PVOH and LCNF mixed solution concentration and LCNF addition ratio, and decreasing lignin content. Scanning electron micrographs revealed that the diameter of the electrospun nanofibers increased as the mixed solution concentration and LCNFs addition increased, the lignin content decreased, and with the homogenization treatment.

Comparative study of cellulose and lignocellulose nanopapers prepared from hard wood pulps: Morphological, structural and barrier properties

The current research intended to explore the hardwood pulps capabilities to produce cellulose (CNPs) and lignocellulose nanopapers (LNPs) and feasible enhancement of their performance for possible utilization in sustainable packaging. The high-yield hardwood pulps were then bleached to show the fundamental role of residual lignin on the ultrafine fibrillation processes, structural and barrier properties of nanopapers. X-ray diffraction results demonstrated that the crystallinity and crystallite size of CNPs and LNPs were lower than the corresponding starting pulps. Field emission scanning electron microscopy analysis showed that the average nanofibril diameter of the CNPs and LNPs are 35 nm and 23 nm, respectively. Elastic modulus of LNPs was found to be 9.1 and 10.8 GPa for Chemimechanical and Neutral sulfite semichemical pulps, respectively. The semi-porous and consolidated structure of LNPs prepared from CMP fibers contributed to yield the lowest water vapor transmission rate i.e. 108 g/m2.day which is promising for potential applications in packaging materials.

Abstract 731: Biophysical Properties of Nanofibrillar Scaffolds Modulate Endothelial Cell Survival in the Ischemic Hind Limb

Research Background and Objectives: Endothelial cells (ECs) are a promising cell type for the treatment of peripheral arterial disease (PAD). We previously showed that anisotropic nanofibrillar scaffolds augment the angiogenic function of ECs. Here we reported the effect of nanofibril size and crosslinking on EC survival and function to optimize the biophysical properties of scaffolds for treatment of PAD. Methods: Aligned nanofibrillar collagen scaffolds of varying fibril diameters and stiffness were prepared by altering the ionic strength (IS) of monomeric collagen and then crosslinked at varying levels of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC). Scaffolds were characterized for surface topography and nanofibril diameter by atomic force microscopy (AFM). Primary human ECs seeded onto the scaffolds were assessed for migration and survival under hypoxia. The regenerative potential of EC-seeded scaffolds was examined in a mouse hind limb ischemia (HLI) model. Results: Scaffold formulation with varying ionic strength (IS) resulted in different fibril diameter regardless of the degree of crosslinking ( Figure 1A: ~100 nm in low IS group vs. ~200 nm in high IS groups). When cultured under hypoxia, ECs seeded on high IS scaffold crosslinked by 1xEDC exhibited improved survival compared to those on low IS. Accordingly, the high IS 1xEDC scaffold was selectively tested in a mouse HLI model for cell survival and blood perfusion restoration. Bioluminescently-tagged ECs were seeded onto high IS 1xEDC scaffold or a randomly oriented fibrillar scaffold (20 mm of each). Non-invasive bioluminescence imaging for quantification of viable cells demonstrated markedly higher cell survival on aligned nanofibrillar scaffold than on randomly oriented scaffold ( Figure 1B, C ). Significance: Aligned nanofibrillar scaffolds that improve survival and angiogenesis of ECs provide a viable clinical strategy for the therapeutic neovascularization.

Influence of combined mechanical treatments on the morphology and structure of cellulose nanofibrils: Thermal and mechanical properties of the resulting films

The deconstruction of the hierarchical structure of cellulose results in the production of cellulose nanofibrils (CNFs). CNFs are commonly obtained by grinding and high-pressure homogenization processes and both treatments can be simultaneously used. Nevertheless, the influence of a two-stage high pressure homogenization of previously ground CNFs on the nanofibril diameter and the physical, thermal and mechanical properties of the resulting films has not been reported. The present study aims at understanding the changes exerted in cellulose after grinding and subsequent passing through the first and second stage of a high-pressure homogenizer. The films prepared from the resulting CNFs were analyzed by electron microscopy, infrared spectroscopy, X-ray diffraction, viscometry, thermal degradation and tensile tests. The data indicate that the initial grinding treatment prompted the most remarkable changes, resulting in enhanced mechanical properties of the films, while decreasing its thermal stability, intrinsic viscosity and crystallinity. Further fibrillation in a high-pressure homogenizer did not have a significant effect, except a decrease in thermal stability and intrinsic viscosity.

Probing the Roles of Polymeric Separators in Lithium-Ion Battery Capacity Fade at Elevated Temperatures

The high temperature mechanical property of separators is very important for safety of lithium-ion batteries. However, the mechanical integrity of polymeric separators in lithium-ion batteries at elevated temperatures is still not well characterized. In this paper, the temperature dependent micro-scale morphology change of PP (polypropylene)-PE (polyethylene)-PP sandwiched separators (Celgard 2325) was studied by in-situ high temperature surface imaging using an atomic force microscope (AFM) coupled with power spectral density (PSD) analysis and digital image correlation (DIC) technique. Both PSD and DIC analysis results show that the PP phase significantly closes its pores by means of dilation of the nanofibrils surrounding the pores in the transverse direction and shrinkage in the machine direction, when cycled at 90°C, even below the separator's shutdown temperature (∼120°C) and its own melting temperature (165°C). This is presumably due to surface melting effect in nanostructures and should be size dependent–the surface melting temperature may decrease with the diameter of nanofibrils. Therefore, some pore closing might happen even at operating temperatures, it will lead to capacity fade that is undesired for battery performance.

High modulus and low-voltage driving nematic liquid-crystalline physical gels for light-scattering displays

Liquid-crystalline (LC) physical gels with a high modulus and low driving voltage were prepared through the self-assembly of sorbitol derivatives as gelators in a nematic liquid crystal, 4-pentyl-4′-cyanobiphenyl (5CB). The structural difference among the used gelators, i.e. 1,3:2,4-di-O-benzylidene-D-sorbitol (DBS), 1,3:2,4-di-O-p-methylbenzylidene-D-sorbitol (MDBS) and 1,3:2,4-di-O-m,p-dimethylbenzylidene-D-sorbitol (DMDBS), is only the number of methyl groups on their phenyl rings. The phase transition temperature, mechanical and electro-optical properties of three LC gels were systematically investigated. Compared with DBS, MDBS and DMDBS with methyl groups on phenyl rings have higher gelation ability in 5CB. The three LC gels exhibit good self-supporting ability with storage moduli higher than 104 Pa when the gelator content is increased to 1.5 wt%. At 3.0 wt% and a gelator content less than 1.0 wt%, both moduli of MDBS and DMDBS gels are obviously higher than that of DBS gel due to the enhanced reinforcement of the more rigid, thicker nano-fibrils and the formed nano-fibrillar network texture in MDBS and DMDBS gels. Also, the driving voltages of LC gels decrease in the order of DBS, MDBS and DMDBS gels with increase of LC domain size and nano-fibril diameter. For DMDBS gel with 3.0 wt% gelators, the threshold voltage and saturation voltage are only 0.5 and 3.5 V μm−1, showing its potential application in self-supporting light-scattering electro-optical displays.

Chemical composition of grape stalks of Vitis vinifera L. from red grape pomaces

The chemical composition and the structure of macromolecular components of grape stalks from red grape pomaces have been evaluated. These are composed mainly of cellulose (30.3%), hemicelluloses (21.0%), lignin (17.4%), tannins (15.9%) and proteins (6.1%). Among hemicelluloses the xylan was the most abundant (ca. 12%). The parameters of cellulose unitary cell, average diameter of nanofibrils and the degree of crystallinity (75.4%) were assessed by X-ray scattering analysis. The xylan was partially acetylated glucuronoxylan (DS = 0.49) possessing the Xyl p:MeGlc pA ratio of 25:1. The lignin of grape stalks was suggested to be of HGS type with H:G:S molar proportion of 3:71:26 as revealed by analysis of nitrobenzene oxidation products. Among alkali soluble condensed tannins procyanidins prevailed over prodelphinidins. The abnormal response of grape stalks to kraft pulping, leading to poorly delignified fibrous material, was attributed to a particular lignin structure and it structural association with other macromolecular components of grape stalks.

Films made of cellulose nanofibrils: surface modification by adsorption of a cationic surfactant and characterization by computer-assisted electron microscopy

Films made of nanofibrils were modified by adsorption of a cationic surfactant directly on the film surfaces. The nanofibrils were prepared by 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation and mechanical fibrillation, and were relatively homogeneous in size. The average nanofibril diameter and surface porosity was quantified based on computer-assisted field-emission scanning electron microscopy (FE-SEM). The cationic surfactant used in the adsorption was n-hexadecyl trimethylammonium bromide (cetyltrimethylammonium bromide, CTAB). The adsorption of CTAB was confirmed by Fourier transform infrared (FTIR) spectroscopy and high-resolution transmission electron microscopy (HRTEM) analyses. It was shown that the adsorbed layer of CTAB increased the hydrophobicity, without affecting the tensile index significantly. This capability, combined with the antiseptic properties of CTAB, may be a major advantage for several applications.

Supercontraction on cribellate spider spiral silk with wet-rebuilt micro-structure

Spiral silk from cribellate spider is a useful material with high viscidity and high elastic properties. In this work, supercontraction of cribellate spiral silk was studied in different air humidity. Humidity is implicated in the re-building of micro-structure and morphology of spiral silk, including the changes of the length and the diameter of nanofibrils. The study suggests that air humidity in the biomimetic thread process can tune the strength and micro-structure of fibers.

Differential adhesion of fibroblast and neuroblastoma cells on size- and geometry-controlled nanofibrils of the extracellular matrix

We present a universal method to produce highly regular arrays of nanofibrils constituted by the extracellular matrix (ECM) proteins fibronectin (FN), collagen I (COL I) and EHS laminin (EHS LN). Adjusting the de-wetting parameters of a protein solution on a hydrophobic silicon micropillar structure, we control the mean nanofibril diameter between 20 nm and 160 nm. Array geometry predetermines nanofibril diameter, while protein concentration and de-wetting speed have to be adapted to yield high regularity. ECM nanofibrils span the space between adjacent pillars and immunofluorescence labelling of LN and FN nanofibrils allows us to discriminate both species in mixed networks. The biological function of ECM nanofibrils was verified in cell adhesion experiments after transfer of the nanofibrils onto non-adhesive polyethylene glycol (PEG) hydrogels. Co-cultures of fibroblasts and neuroblastoma cells on vertically arranged nanofibrils of FN and LN showed differential adhesion of the distinct cell types.