Dissolution Of Fibers Research Articles

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials.

Biopersistence and biodurability have the potential to influence the long-term toxicity and hence pathogenicity of particles that deposit in the body. Therefore, biopersistence and biodurability are considered to be important parameters needed for the risk assessment of particles and fibres. Dissolution, as a measure of biodurability, is dependent on the chemical and physical properties (size, surface area, etc.) of particles and fibres and also of the suspension medium including its ionic strength, pH, and temperature. In vitro dissolution tests can provide useful insights as to how particles and fibres may react in biological environments; particles and fibres that release ions at a higher rate when suspended in vitro in a specific simulated biological fluid will be expected to do so when they exist in a similar biological environment in vivo. Dissolution of particles and fibres can follow different reaction kinetics. For example, the majority of micro-sized particles and fibres follow zero-order reaction kinetics. In this case, although it is possible to calculate the half-time of a particle or fibre, such calculation will be dependent on the initial concentration of the investigated particle or fibre. Such dependence was eliminated in the shrinking sphere and fibre models where it was possible to estimate the lifetimes of particles and fibres as a measure of their biodurability. The latter models can be adapted for the dissolution studies of nanomaterials. However, the models may apply only to nanomaterials where their dissolution follows zero-order kinetics. The dissolution of most nanomaterials follows first-order kinetics where dependence on their initial concentration of the investigated nanomaterials is not required and therefore it is possible to estimate their half-times as a measure of their biodurability. In dissolution kinetics for micro-sized and nano-sized particles and fibres, knowledge of dissolution rate constants is necessary to understand biodurability. Unfortunately, many studies on dissolution of nanoparticles and nanofibres do not determine the dissolution rates and dissolution rate constants. The recommendation is that these parameters should be considered as part of the important descriptors of particle and fibre physicochemical properties, which in turn, will enable the determination of their biodurability.

Effect of supercritical fluid activation on the diameter of carbon fibres

This work is a comparative study of the variations in the structure of a carbon fibre activated with supercritical H2O and CO2 vs. steam and CO2 at atmospheric pressure (conventional process). The appearances of the external and internal surfaces, fibre size, external and internal mass loss, density, porosity, and fragmentation, etc. were measured and analysed. The results are explained by the different reactivity of the supercritical fluids compared with the steam and CO2 at atmospheric pressure. The results are coherent with a gasification model based on percolation theory, and special emphasis is given to fibre disintegration once the carbonaceous matrix porosity has reached a critical value.

Schip1 is a novel podocyte foot process protein that mediates actin cytoskeleton rearrangements and forms a complex with Nherf2 and ezrin.

BackgroundPodocyte foot process effacement accompanied by actin cytoskeleton rearrangements is a cardinal feature of many progressive human proteinuric diseases.ResultsBy microarray profiling of mouse glomerulus, SCHIP1 emerged as one of the most highly enriched transcripts. We detected Schip1 protein in the kidney glomerulus, specifically in podocytes foot processes. Functionally, Schip1 inactivation in zebrafish by morpholino knock-down results in foot process disorganization and podocyte loss leading to proteinuria. In cultured podocytes Schip1 localizes to cortical actin-rich regions of lamellipodia, where it forms a complex with Nherf2 and ezrin, proteins known to participate in actin remodeling stimulated by PDGFβ signaling. Mechanistically, overexpression of Schip1 in vitro causes accumulation of cortical F-actin with dissolution of transversal stress fibers and promotes cell migration in response to PDGF-BB stimulation. Upon actin disassembly by latrunculin A treatment, Schip1 remains associated with the residual F-actin-containing structures, suggesting a functional connection with actin cytoskeleton possibly via its interaction partners. A similar assay with cytochalasin D points to stabilization of cortical actin cytoskeleton in Schip1 overexpressing cells by attenuation of actin depolymerisation.ConclusionsSchip1 is a novel glomerular protein predominantly expressed in podocytes, necessary for the zebrafish pronephros development and function. Schip1 associates with the cortical actin cytoskeleton network and modulates its dynamics in response to PDGF signaling via interaction with the Nherf2/ezrin complex. Its implication in proteinuric diseases remains to be further investigated.

Uniaxial load analysis under stretch-dependent fiber remodeling applicable to collagenous tissue

This article investigates the relation between stress and deformation of a fibrous material that is subjected to a constant fiber creation rate and deformation-dependent fiber dissolution rate. Experimental studies show such behavior in certain highly collagenous tissue. The investigation focuses on two different constitutive hypotheses: (a) fibers that reassemble in an undeformed state and (b) fibers that reassemble in a pre-strained state that is equal to the strain state of the surrounding matrix. The matrix component of the material is treated as isotropic and hyperelastic, and its mechanical properties remain constant in time. Separate processes of step displacement and step load are considered. In each case, an initial state of homeostasis is disrupted by the step input. The system then evolves to a new state of homeostasis that can be predicted in advance. The approach to this new homeostasis requires the consideration of a Volterra-type integral equation.

RhoD is a Golgi component with a role in anterograde protein transport from the ER to the plasma membrane

RhoD is a member of the Rho GTPase family and it coordinates actin dynamics and membrane trafficking. Activation of RhoD results in formation of filopodia, dissolution of stress fibers, and the subsequent formation of short actin bundles. In addition, RhoD localizes to early endosomes and recycling endosomes, and has a regulatory role in endosome trafficking. In this study, we report on a function of RhoD in the regulation of Golgi homeostasis. We show that manipulation of protein and activation levels of RhoD, as well as of its binding partner WHAMM, result in derailed localization of Golgi stacks. Moreover, vesicle trafficking from the endoplasmic reticulum to the plasma membrane via the Golgi apparatus measured by the VSV-G protein is severely hampered by manipulation of RhoD or WHAMM. In summary, our studies demonstrate a novel role for this member of the Rho GTPases in the regulation of Golgi function.

Optimization of spinning parameters influencing the characteristics of structurally modified viscose yarn

Yarn structure influences the configuration of the constituent fibers in the yarn and the comfort properties of the fabrics to a great extent. The fiber arrangement in the yarn has a major influence on the comfort-related properties such as thermal conductivity, air permeability, wickability, and moisture vapor permeability. This study dealt with the influence of process and material variables namely, polyvinyl alcohol (PVA) proportion, twist multiplier (TM), and spindle speed on microporous viscose yarn properties. Three-variable three-factor Box and Behnken method was used to investigate the individual and interaction effects of selected variables on yarn properties. The selected variables have a significant influence on all the yarn properties. The increase in PVA%, spindle speed, and TM reduces the specific volume and wickability of yarns and increases the tenacity and packing factor of yarns before dissolving the PVA fibers. With increase in spindle speed and TM, same trend was noticed after dissolving the PVA also. But the trend reverses with increase in PVA percentage after dissolution of PVA fiber. The increase in PVA percentage increases the specific volume and wickability of yarns and decreases the tenacity and packing factor of yarns after dissolution of PVA fiber. The optimized process parameters were obtained, and yarn was spun with the optimized parameters to validate the model.

Hypertrophic lichen sclerosus sine sclerosis: clues to histopathologic diagnosis when presenting as psoriasiform lichenoid dermatitis.

The histopathologic diagnosis of lichen sclerosus (LS) is usually facilitated by a subepidermal zone of sclerosis. In the absence of sclerosis, LS mostly presents itself as a psoriasiform lichenoid dermatitis that may be difficult to distinguish from other diseases. We sought to assess histopathologic findings that allow recognition of LS in the absence of sclerosis. We studied 28 criteria in 100 biopsy specimens of LS from genital or perianal skin, including 55 cases with marked sclerosis, 16 cases with mild sclerosis confined to foci of the papillary dermis and 29 cases without sclerosis. Fifteen cases each of the early plaque stage of mycosis fungoides, lichen planus and lichen simplex chronicus were studied for comparison. Some histopathologic hallmarks of LS were seen chiefly in sclerotic lesions and, therefore, did not contribute to the diagnosis of difficult cases, such as dissolution of elastic fibers. Others were seen rarely in non-sclerotic lesions but might be helpful in individual cases, including follicular hyperkeratosis and thickening of the basement membrane. Findings that were more common and may be utilized as clues to the histopathologic diagnosis of non-sclerotic LS include tiny foci of homogenized tissue in dermal papillae, marked fibrosis with thickening of the papillary dermis, marked thickening of individual collagen fibers, lymphocytes aligned in rows between those fibers, necrotic keratinocytes, often with preserved pyknotic nuclei, in all reaches of the epidermis, including the cornified layer, clustering of necrotic keratinocytes above elongated dermal papillae and vertical columns of parakeratosis with distinct dyskeratotic parakeratotic cells. In the absence of sclerosis, histopathologic diagnosis of LS depends on findings that are less distinctive. Nonetheless, a constellation of those findings allows a specific diagnosis to be made.

Star-pseudopolyrotaxane organized in nanoplatelets for poly(ε-caprolactone)-based nanofibrous scaffolds with enhanced surface reactivity.

Herein, it is demonstrated that star pseudopolyrotaxanes (star-pPRs) obtained from the inclusion complexation of α-cyclodextrin (CD) and four-branched star poly(ε-caprolactone) (star-PCL) organize into nanoplatelets in dimethyl sulfoxide at 35 °C. This peculiar property, not observed for linear pseudopolyrotaxanes, allows the processing of star-pPRs while preserving their supramolecular assembly. Thus, original PCL:star-pPR core:shell nanofibers are elaborated by coaxial electrospinning. The star-pPR shell ensures the presence of available CD hydroxyl functions on the fiber surface allowing its postfunctionalization. As proof of concept, fluorescein isothiocyanate is grafted. Moreover, the morphology of the fibers is maintained due to the star-pPR shell that acts as a shield, preventing the fiber dissolution during chemical modification. The proposed strategy is simple and avoids the synthesis of polyrotaxanes, i.e., pPR end-capping to prevent the CD dethreading. As PCL is widely used for biomedical applications, this strategy paves the way for simple functionalization with any bioactive molecules.

In vitro and in vivo characterization of the actin polymerizing compound chondramide as an angiogenic inhibitor.

Inhibiting angiogenesis is a major approach in tumour therapy. To combat angiogenesis, the tubulin cytoskeleton has emerged as an interesting target in many pre- and clinical studies. Contrarily, the actin cytoskeleton has been largely neglected as a potential drug target in angiogenesis. However, due to the development of drug resistances, new therapeutic strategies are always needed in tumour treatment. Therefore, the therapeutic potential of actin-binding small molecules is of particular interest. We investigate the impact of chondramide (Ch), an actin polymerizing myxobacterial compound, on angiogenesis and underlying signalling. Chondramide treatment not only reduces the migration of endothelial cells but also the maturation of endothelial tube networks on matrigel. These observations can partly be explained by a disintegration of stress fibres due to aggregation and subsequent accumulation of actin in cellular structures known as 'aggresomes'. Chondramide treatment impairs the maturation of focal adhesions and reduces the amount of active β1 integrin at the cell surface. Accordingly, signalling events downstream of focal adhesions are reduced. Thus, we observed that the activity of Src and downstream factors Rho-GTPases Rac1 and Rho is reduced upon Ch treatment. In vivo, Ch was well tolerated in mice and vascularization of a tumour xenograft as well as of the developing retina was significantly reduced. Chondramide diminishes angiogenesis via two ways: (i) the disintegration of stress fibres and (ii) the reduction of promigratory signals. Our findings highlight Ch as a novel class of therapeutic lead compound with anti-angiogenic potential.

Toxicological and epidemiological studies on effects of airborne fibers: Coherence and public health implications

Airborne fibers, when sufficiently biopersistent, can cause chronic pleural diseases, as well as excess pulmonary fibrosis and lung cancers. Mesothelioma and pleural plaques are caused by biopersistent fibers thinner than ∼0.1 μm and longer than ∼5 μm. Excess lung cancer and pulmonary fibrosis are caused by biopersistent fibers that are longer than ∼20 μm. While biopersistence varies with fiber type, all amphibole and erionite fibers are sufficiently biopersistent to cause pathogenic effects, while the greater in vivo solubility of chrysotile fibers makes them somewhat less causal for the lung diseases, and much less causal for the pleural diseases. Most synthetic vitreous fibers are more soluble in vivo than chrysotile, and pose little, if any, health pulmonary or pleural health risk, but some specialty SVFs were sufficiently biopersistent to cause pathogenic effects in animal studies. My conclusions are based on the following: 1) epidemiologic studies that specified the origin of the fibers by type, and especially those that identified their fiber length and diameter distributions; 2) laboratory-based toxicologic studies involving fiber size characterization and/or dissolution rates and long-term observation of biological responses; and 3) the largely coherent findings of the epidemiology and the toxicology. The strong dependence of effects on fiber diameter, length, and biopersistence makes reliable routine quantitative exposure and risk assessment impractical in some cases, since it would require transmission electronic microscopic examination, of representative membrane filter samples, for determining statistically sufficient numbers of fibers longer than 5 and 20 μm, and those thinner than 0.1 μm, based on the fiber types.

What Happens during Natural Protein Fibre Dissolution in Ionic Liquids.

Here, we monitor the dissolution of several natural protein fibres such as wool, human hair and silk, in various ionic liquids (ILs). The dissolution of protein-based materials using ILs is an emerging area exploring the production of new materials from waste products. Wool is a keratin fibre, which is extensively used in the textiles industry and as a result has considerable amounts of waste produced each year. Wool, along with human hair, has a unique morphology whereby the outer layer, the cuticle, is heavily cross linked with disulphide bonds, whereas silk does not have this outer layer. Here we show how ILs dissolve natural protein fibres and how the mechanism of dissolution is directly related to the structure and morphology of the wool fibre.

Dissolution of rayon fibers for size exclusion chromatography: a challenge

Application of size exclusion chromatography (SEC) for the analysis of cellulose samples is often limited due to poor solubility in the solvent system N,N-dimethylacetamide/lithium chloride (DMAc/LiCl). Hence different activation or derivatization methods have been developed and published. Most of these methods are laborious, influence the molar mass distribution or do not support dissolution of manmade fibers, such as viscose rayon. In this study, we have evaluated different activation methods for their applicability in viscose rayon dissolution and we present a novel method for activation. We found that an additional solvent exchange step with dimethyl sulfoxide (DMSO) increases and accelerates solubility of viscose fibers in DMAc/LiCl for subsequent SEC analysis. The improved dissolution by DMSO activation is mainly due to increased swelling and improved action towards the outer skin of the fiber. The novel approach has also been applied to the even more difficult dissolution of oxidized viscose fibers.

Mechanical Characterization of Brown and Green Coconut Husk

The mechanical properties of both brown and green coconut husk were evaluated by using Universal Testing Machine (UTM). Different auxiliary tools were employed for gripping and mounting the peculiar shaped coconut husk on to the machine. Tensile and compression test (both in longitudinal and transverse direction), tear strength, and U-bend test of the husk were carried out. Husk offered maximum resistance in longitudinal direction of tensile load and in the transverse direction for compression load. Husk disintegration is easy in longitudinal direction. The green husk was found stable to deformation and resilient as compared to brown husk, thus needing less beating force for fiber disintegration.

Dissolution of serpentine fibers under acidic flotation conditions reduces inter-fiber friction and alleviates impact of pulp rheological behavior on Ni ore beneficiation

In beneficiation of Ni ores containing fibrous serpentines in large amounts, flotation pulps exhibit high viscosity, impacting Ni recovery and grade. Fibers entangle in pulp with formation of inter-fiber networks made up of micro floccs that spread across the pulp volume. These networks are sturdy and difficult to disentangle as inter-fiber frictional forces which are the predominant among the inter-particle forces restrict sliding of fibers at the inter-fiber contact points. The net force from numerous contact points in a network is significant. Therefore, the pulp yield stress value, a measure of net inter-particle forces, is considerably higher than that is typical in flotation. According to this study, the pulp yield stress decreases upon addition of H2SO4 to the pulp, which also correlates to the extent of serpentine dissolution. The continuation of fiber dissolution is necessary to maintain the inter-fiber frictional forces to a lower value, and serves as an inter-fiber lubricant for loosening of these networks. Thus, acidic conditions alleviate the impact of pulp rheological behavior on Ni ore beneficiation.

Effect of boron oxide addition on fibre drawing, mechanical properties and dissolution behaviour of phosphate-based glass fibres with fixed 40, 45 and 50 mol% P2O5.

Previous studies investigating manufacture of phosphate-based glass fibres from glasses fixed with P2O5 content less than 50 mol% showed that continuous manufacture without breakage was very difficult. In this study, nine phosphate-based glass formulations from the system P2O5-CaO-Na2O-MgO-B2O3 were prepared with P2O5 contents fixed at 40, 45 and 50 mol%, where Na2O was replaced by 5 and 10 mol% B2O3 and MgO and CaO were fixed to 24 and 16 mol%, respectively. The effect of B2O3 addition on the fibre drawing, fibre mechanical properties and dissolution behaviour was investigated. It was found that addition of 5 and 10 mol% B2O3 enabled successful drawing of continuous fibres from glasses with phosphate (P2O5) contents fixed at 40, 45 and 50 mol%. The mechanical properties of the fibres were found to significantly increase with increasing B2O3 content. The highest tensile strength (1200 ± 130 MPa) was recorded for 45P2O5-16CaO-5Na2O-24MgO-10B2O3 glass fibres. The fibres were annealed, and a comparison of the mechanical properties and mode of degradation of annealed and non-annealed fibres were investigated. A decrease in tensile strength and an increase in tensile modulus were observed for the annealed fibres. An assessment of the change in mechanical properties of both the annealed and non-annealed fibres was performed in phosphate-buffered saline (PBS) at 37℃ for 28 and 60 days, respectively. Initial loss of mechanical properties due to annealing was found to be recovered with degradation. The B2O3-containing glass fibres were found to degrade at a much slower rate as compared to the non-B2O3-containing fibres. Both annealed and non-annealed fibres exhibited a peeling effect of the fibre's outer layer during degradation.

A theory for deformation dependent evolution of continuous fibre distribution applicable to collagen remodelling

This work explores the implications of a constitutive framework that introduces a particular remodelling process for materials having a continuous distribution of fibre directions. It is assumed that the matrix constituent is unaffected and that fibres remodel by a process of dissolution and reassembly. Dissolution results from a time dependent chemical kinetic process that is influenced by fibre stretch. Two possibilities for the reassembly of the fibres are considered: (1) fibres reassemble in a stress-free state or (2) fibres assemble in a pre-strained state matching that of the surrounding matrix. The composite is treated as a non-linear hyperelastic material. The constitutive framework accounts for the time dependent redistribution of fibre orientation and density. A directional fibre orientation density function is defined that combines fibre dissolution, reassembly and their dependence on deformation history. Expressions for the time dependence of this function are developed for the two fibre reassembly assumptions and different deformation histories. Numerical results for uniaxial extension are presented in the form of polar plots that illustrate fibre orientation density at different times and fibre density versus time plots that show evolution at different orientations.

Effect of NaOH/urea solution on enhancing grease resistance and strength of paper

Abstract A new way as shown in the following scheme was developed to fabricate paper with high strength and grease resistance. Filter paper was impregnated in NaOH/urea aqueous solution pre-cooled to -12°C for 30 s and incubated at a fixed temperature for a period of time. Swelling and dissolution of cellulose fibers facilitated more compact structure of paper and higher strength. Various influencing factors were investigated in an attempt to improve grease resistance of the paper. The results demonstrated that the paper after treatment showed a 100% grease barrier property within 24 h, and a double increase in both tensile strength and tear strength compared with the untreated paper. Moreover, burst strength was enhanced more than three times and the stretch was improved simultaneously when the paper was performed with NaOH/urea (7%:12% weight ratio) at -12°C for 120 min. In addition, the wet tensile strength of the treated paper was close to the dry tensile strength of the untreated paper.

Residual performance of a silyl-modified polymer adhesive for CFRP-steel interface exposed to thermally-induced stress states

This paper presents an experimental program evaluating the residual behavior of carbon fiber reinforced polymer (CFRP)-steel interface bonded with a silyl-modified polymer (SMP) adhesive when subjected to thermally-induced stress states. A total of 40 specimens are prepared and exposed to elevated temperatures from 25°C to 200°C. According to test results, interfacial capacity is well maintained up to a temperature of 100°C; however, thermal hysteresis takes place beyond 100°C. Exposure temperatures higher than 175°C result in a phase-transition of the adhesive morphology during heating and influence the adhesion characteristics of the bonding agent. Geometric discontinuities along the interface affect CFRP-strain development and a shear-lag mechanism is noticed, which is virtually independent of the degree of thermal exposure. Fiber disintegration is the primary failure mode of the interface up to 150°C, including intricate local fiber dislocation and partial CFRP pull-out. The specimens exposed to temperatures higher than 175°C revealed a simple CFRP-debonding failure mode due to the thermal damage of the SMP. A probabilistic approach is taken to complement the experimental observation. The probability of the CFRP-steel interface tested is found to be normally distributed. The Bayesian updating method probabilistically infers the thermal characteristics of the interface with emphasis on temperature-dependent interfacial fracture energy. Design properties are proposed for practical application of the CFRP-steel interface with SMP.

A methodology to orient carbon nanotubes in a thermosetting matrix

Abstract A new procedure for the alignment of carbon nanotubes in a thermosetting matrix is proposed in this study. The two-step approach is based on (i) the alignment of carbon nanotubes (CNTs) in thermoplastic fibres by electrospinning and (ii) the transfer of these nanocompositefibres into a reactive thermosetting resin, in which they are easily soluble. After fibre dissolution, the CNTs remain aligned in the cured thermosetting matrix. The proof of concept is demonstrated by producing electrospunpolymethyl methacrylate (PMMA) fibres filled with single wall carbon nanotubes (SWCNTs) in the form of unidirectional tape, which are then solubilised into a vinylester (VE) matrix. The PMMA is easily dissolved by the styrene present in the VE resin, leaving SWCNTs aligned in the cured VE network, as confirmed by Raman spectroscopy studies. A 50% increase in elastic modulus (SWCNT 1.3 wt.%) has been obtained by dynamic mechanical analysis carried out in tensile mode at 1 Hz. Thanks to its ability to orient carbon nanotubes in a thermosetting matrix, the proposed method can be exploited also to transfer oriented nanofillers into continuous fibre composites, thus obtaining multiscale or hierarchical composites.

Hydrophobization and characterization of internally crosslink-reinforced cellulose fibers

Transforming hydrophilic cellulose fibers into hydrophobic, non-hygroscopic fibers could potentially lead to a variety of new products, such as flexible packaging, self-cleaning films and strength-enhancing agents in polymer composites. To achieve this, softwood cellulose pulp was chemically modified with successive chemical treatments. First the C2 and C3 hydroxyl groups of the glucose units were selectively oxidized by periodate oxidation to reactive dialdehyde units on the cellulose chain, followed by a Schiff base reaction with 1,12-diaminododecane to crosslink the microfibrils within the fiber wall. This was done, because introducing high levels of alkylation resulted in fiber disintegration, which could be prevented by crosslinking. After internal crosslinking a second Schiff base reaction was performed with butylamine. This procedure yielded highly hydrophobic and low-hygroscopic cellulosic materials. The modified cellulose fibers were investigated by a variety of techniques, including Fourier transform infrared spectroscopy, nuclear magnetic resonance, field-emission scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, moisture sorption and water contact angle measurements. The water uptake of the fibers after being modified reduced from 4 to around 1 %. Various reaction conditions were studied for optimum performance.