Fibrous System Research Articles

Blend fibers of chitosan–agarose by electrospinning

A novel fibrous system, chitosan/agarose, was successfully developed via the electrospinning of their blend solutions. The trifluoroacetic acid (TFA)/dichloromethane (DCM) mixture was used as a suitable solvent for both chitosan and agarose. It was found that smooth, continuous fibers were generated at an agarose content of less than 50%. Moreover, with the increase of the agarose content from zero to 50%, the average diameter of the fibers was significantly decreased from about 1.76 to 0.14 μm. The FT-IR analysis revealed a gradual shift of the absorption band in the blend fibers, suggesting the strong interaction and good compatibility between chitosan and agarose.

Luffa cylindrica - An emerging cash crop

Sponge-gourds, the fruit of Luffa cylindrica, are widely used throughout the world. It is an annual climbing crop which produces fruit containing fibrous vascular system. It is a summer season vegetable. At the moment, from the results of studies carried out on this wonder crop, it encourages the commercial cultivation of the crop because of its increasing economic importance. The objective of this review is to show the potentialities of this crop that is virtually found around the globe. Areas such as agriculture, medicine, science, engineering and biotechnology will be discussed. Recent major advances and discoveries will be considered.

Tailoring the Properties of Guanosine-Based Supramolecular Hydrogels

We demonstrate that very stable hydrogels can be formed in aqueous potassium chloride solution by mixing a well-known gelator (guanosine, G) with a nongelator of similar structure (2',3',5'-tri-O-acetylguanosine, TAcG), and through a variety of characterization methods including rheology, small-angle neutron scattering, differential scanning calorimetry, and atomic force microscopy, we report substantial progress toward elucidating the factors that control the structure and stability of this fibrous gel system. The results suggest that the tailorability, long lifetime stability, and thermomechanical behavior of these gels derives from a reduction in the driving force toward crystallization with increased hydrophobic (TAcG) content, accompanied by a simultaneous decrease in fiber length and an increase in fiber width.

On a semi-infinite crack penetrating a piezoelectric circular inhomogeneity with a viscous interface

We investigate a semi-infinite crack penetrating a piezoelectric circular inhomogeneity bonded to an infinite piezoelectric matrix through a linear viscous interface. The tip of the crack is at the center of the circular inhomogeneity. By means of the complex variable and conformal mapping methods, exact closed-form solutions in terms of elementary functions are derived for the following three loading cases: (i) nominal Mode-III stress and electric displacement intensity factors at infinity; (ii) a piezoelectric screw dislocation located in the unbounded matrix; and (iii) a piezoelectric screw dislocation located in the inhomogeneity. The time-dependent electroelastic field in the cracked composite system is obtained. Particularly the time-dependent stress and electric displacement intensity factors at the crack tip, jumps in the displacement and electric potential across the crack surfaces, displacement jump across the viscous interface, and image force acting on the piezoelectric screw dislocation are all derived. It is found that the value of the relaxation (or characteristic) time for this cracked composite system is just twice as that for the same fibrous composite system without crack. Finally, we extend the methods to the more general scenario where a semi-infinite wedge crack is within the inhomogeneity/matrix composite system with a viscous interface.

Immobilization of Oligostyrene-Prolinol Conjugates into Polystyrene via Electrospinning and Applications of these Fibers in Catalysis

This paper reports the synthesis of prolinol-oligostytrene conjugates and their immobilization into a polystyrene matrix by using the electrospinning process. Via this approach fibers with a large surface area (fiber diameter of 1.2 µm) containing the prolinol conjugate are readily obtained. The fibers are shown to be catalytically active in a test Michael reaction. The fibrous catalyst system can readily be removed from the reaction mixture and be reused. However, a decrease of the catalyst activity was noticed upon recycling the fibrous catalyst systems.

A two-stage perfusion fibrous bed bioreactor system for mass production of embryonic stem cells

Background: Embryonic stem cells (ESCs) have unlimited proliferation potential and can differentiate into all cell and tissue types, and thus are ideal sources for cell therapy and drug screening. Current supplies of ESCs are limited by the available cell sources and inefficient culture methods that grow ESCs on surfaces coated with expensive extracellular matrix (ECM) proteins and in media containing expensive growth factors. Objective: To meet the demand for ESCs, it is necessary to develop an economical process for their mass production. Methods: We review the latest development in in vitro ESC culture and introduce a two-stage perfusion bioreactor system that uses 3-D fibrous matrices and conditioned media for production of ESCs. Results/conclusion: The two-stage process can produce billions of ESCs in a small bioreactor without using ECM proteins and growth factors, and is promising for further scale-up for clinical applications.

Fibrous Reinforcing System to Increase the Shear Resistance of High Strength Concrete

The available research has evidenced that discrete steel fibers can increase significantly the shear resistance of High Strength Concrete (HSC) structural elements when High Strength Fiber Reinforced Concrete (HSFRC) is designed in such way that fiber reinforcing mechanisms are optimized. In general, the increase of the concrete compressive strength is associated to an increase of its compactness, resulting benefits in terms of durability, but a strong concern emerges related to the integrity of this material, since it fails in a too brittle mode when submitted to high temperatures. To contribute for the knowledge about the benefits provided by discrete steel fibers when added to HSC applied to laminar structures, an experimental program composed of slab strips submitted to shear loading configuration was carried out. Uniaxial compression tests with cylinders of 150 mm diameter and 300 mm height, and bending tests with 600×150×150 mm3 beams were executed to assess the compression and bending behavior of the developed HSFRC. To evaluate the influence of the percentage of fibers in the shear resistance of laminar structures, three point loading tests with slab strips of 800×170×150 mm3 dimensions were performed. Taking the obtained experimental results, the applicability of the formulation proposed by RILEM TC 162-TDF was evaluated. Test results showed that, even with relative low dosages of steel fibers, the increment in shear resistance was significantly increased. The main obtained results in the research program are presented and discussed in this paper.

Polymer Fibers as Carriers for Homogeneous Catalysts

This paper describes a polymer fiber-based approach for the immobilization of homogeneous catalysts. The goal is to generate products that are free of catalysts which would be of great importance for the development of optoelectronic or pharmaceutical compounds. Electrospinning was employed to prepare the non-woven fiber assembly composed of polystyrene. The homogeneous catalyst scandium triflate was immobilized on the polystyrene fibers during electrospinning and on corresponding core shell fibers using a fiber template approach. An imino aldol and an aza-Diels-Alder model reaction were carried out with each fibrous catalytic system. This resulted in the immobilization of homogeneous catalysts in a polymer environment without loss of their catalytic activity and may even be enhanced when compared with reactions carried out in homogeneous solutions.

Cover Picture: Assembly and Photoinduced Organization of Mono‐ and Oligopeptide Molecules Containing an Azobenzene Moiety (Adv. Funct. Mater. 9/2007)

AbstractAn illustration of the phototriggered organization and dispersion of tri‐peptide‐substituted azobenzene derivatives, as reported on p. 1507 by Yoko Matsuzawa and co‐workers. The tri‐peptide units form a beta‐sheet structure through hydrogen bonding to assemble a fibrous network system. Cis–trans photoisomerization of the azobenzene moiety leads to a large polarity change of the component molecule to break and re‐form hydrogen bonds between the tri‐peptide units.Assembled systems consisting of an azobenzene moiety as the photofunctional component and valyl units as the network backbone are investigated. The molecular ordering of these assemblies is examined by spectroscopy and theoretical calculations. The number of valyl units greatly influences the molecular order in the organized systems. Only N‐(L‐valyl‐L‐valyl‐L‐valyl)azobenzene‐4‐carboxamide (3) forms a complete β‐sheet structure in this artificial assembly. Upon photoirradiation, the azobenzene moieties isomerize completely, revealing the reversibility in the structural organization through the flexibility of the β‐sheet network in this system.

Dynamics of asymmetrical crack propagation in composite materials

When a crack appears in composite materials, the fibrous system will form bridges, and the crack propagates asymmetrically as a rule. A dynamic model of an asymmetrical crack propagation is considered and investigated by applying the self-similar functions. The formulation involves the development of a Riemann–Hilbert problem. The analytical solution of an asymmetrical propagation crack of composite materials under the action of variable moving loads and unit-step moving loads is obtained.

Proliferation and differentiation of human mesenchymal stem cell encapsulated in polyelectrolyte complexation fibrous scaffold

A biofunctional scaffold was constructed with human mesenchymal stem cells (hMSCs) encapsulated in polyelectrolyte complexation (PEC) fibers. Human MSCs were either encapsulated in PEC fibers and constructed into a fibrous scaffold or seeded on PEC fibrous scaffolds. The proliferation, chondrogenic and osteogenic differentiation of the encapsulated and seeded hMSCs were compared for a culture period of 5.5 weeks. Gene expression and extracellular matrix production showed evidences of chondrogenesis and osteogenesis in the cell-encapsulated scaffolds and cell-seeded scaffolds when the samples were cultured in the chondrogenic and osteogenic differentiation media, respectively. However, better cell proliferation and differentiation were observed on the hMSC-encapsulated scaffolds compared to the hMSC-seeded scaffolds. The study demonstrated that the cell-encapsulated PEC fibers could support proliferation and chondrogenic and osteogenic differentiation of the encapsulated-hMSCs. Together with our previous works, which demonstrated the feasibility of PEC fiber in controlled release of drug, protein and gene delivery, the reported PEC fibrous scaffold system will have the potential in composing a multi-component system for various tissue-engineering applications.

Biomechanics of the Membranous Flexor Tendon Sheath: The Role of Grayson??s Ligaments

The biomechanical integrity of the tendon sheath of the fingers has a significant effect on the success of flexor tendon surgery. As nonweightbearing elements, the membranous parts of the sheath have received little attention, and their contribution to sheath movement is still obscure. The authors presumed that Grayson's ligaments, which have been described as force-transmitting elements, might play a role in the biomechanics of the membranous flexor tendon sheath. Twenty-two long fingers of cadaver hands were examined. The authors studied the movements of the inner aspect of the tendon sheath and the positions and patterns of the septa of the palmar soft tissues on picrosirius red-enhanced sagittal and transverse sections and hematoxylin and eosin-stained light microscopy specimens. The movements of the membranous flexor tendon sheath are controlled by subcutaneous structures. The septal patterns of the palmar fat pads indicate the existence of a highly flexible subcutaneous fibrous system in which the deformable fat pad keeps the force-transmitting elements tight. Collagen bundles in the microscopy specimens, which frequently form layers within the septa, are thought to correspond to Grayson's ligaments. The subcutaneous fibrous system adheres predominantly to the membranous parts of the flexor tendon sheath. Folding of the membranous flexor tendon sheath is guided by the subcutaneous fibrous system, of which the macroscopically dissectible elements are Grayson's ligaments. The current surgical approaches might have a deteriorating effect on the biomechanics of the flexor tendon sheath.

Intrauterine levonorgestrel delivered by a frameless system, combined with systemic estrogen: Acceptability and endometrial safety after 3 years of use in peri- and postmenopausal women

Objective. To evaluate the acceptability and endometrial safety of a novel intrauterine drug delivery system, FibroPlant-levonorgestrel (LNG), combined with estrogen therapy (ET) in 150 peri- and postmenopausal women, followed-up for at least 3 years.Design. This was a prospective, non-comparative study in peri- and postmenopausal women. In the majority of women, treatment with the FibroPlant-LNG intrauterine system (IUS), combined with ET, was initiated during the perimenopausal transitional phase to establish a smooth transition to menopause and suppress the endometrium to prevent endometrial proliferation and bleeding. A 3.5-cm long coaxial fibrous delivery system, delivering approximately 14 μg LNG/day, was used. The calculated duration of release of the system is at least 3 years. The majority of women received percutaneous 17β-estradiol (Oestrogel®), 1.5 mg daily on a continuous basis, which provides sufficient blood levels of estrogen in most women to suppress climacteric symptoms and protect against bone loss.Outcome measures. To measure acceptability, women were asked, after they had the IUS in place for a minimum of 3 years, if they would like to continue the combined regimen and if they would accept renewal of the IUS. Endometrial safety was evaluated by transvaginal ultrasound examination and endometrial biopsy in a subset of 101 women prior to replacement of the IUS.Results. Ninety-four insertions were done in perimenopausal and 56 in postmenopausal women aged between 33 and 78 years. Of the total group of 150 women, 132 women (88.0%) accepted replacement of the IUS and ten are waiting for replacement. This group includes nine women who will receive a second replacement. The number of women continuing the method is 142 (94.6%). Histological examinations conducted on endometrial biopsies from 101 postmenopausal women prior to replacement, after an average period of use of the regimen of 40 months (range 25–50 months), showed predominantly inactive endometrium characterized by pseudodecidual reaction of the endometrial stroma with endometrial atrophia, which is in keeping with the effects seen with a progestogenic compound. There were no specimens showing signs of proliferation.Conclusions. Results suggest that the frameless FibroPlant-LNG IUS is safe, well tolerated, well accepted and effective in suppressing the endometrium during ET. Intrauterine progestogen administration in postmenopausal women can be regarded as fundamentally advantageous compared with systemically applied progestogens, which may have potentially inherent ill side-effects, especially on the breast and cardiovascular system, as reported in the recent literature.

Analysis of the long-term efficacy of interferon therapy for type C chronic hepatitis using a quantitative fibrous scoring system: Mitsuhiko Moriyama, Nihon University Scholl of Medicine, Tokyo 173–8610 Japan; Hiroshi Matsumura, Hiroshi Aoki, Ikuo Miyauchi, Iori Goto, Atsuo Shioda, Miki Kaneko, Nihon University School of Medicine, Tokyo Japan; Yasuyuki Arakawa, Nihon University School of Medicine, Tokyo Japan

Analysis of the long-term efficacy of interferon therapy for type C chronic hepatitis using a quantitative fibrous scoring system: Mitsuhiko Moriyama, Nihon University Scholl of Medicine, Tokyo 173–8610 Japan; Hiroshi Matsumura, Hiroshi Aoki, Ikuo Miyauchi, Iori Goto, Atsuo Shioda, Miki Kaneko, Nihon University School of Medicine, Tokyo Japan; Yasuyuki Arakawa, Nihon University School of Medicine, Tokyo Japan

Continuous combined parenteral estrogen substitution and intrauterine progestogen delivery: the ideal HST combination?

Objective: To evaluate ease of insertion, acceptability and endometrial safety of a novel, miniature intrauterine, T-shaped, levonorgestrel (LNG)-releasing intrauterine system (IUS), Femilis™ Slim LNG-IUS (Contrel Research, Belgium), combined with parenteral estrogen substitution therapy (EST) in postmenopausal women. Design: A prospective, non-comparative, study in postmenopausal women. A 3.0 cm long and 2.0 mm wide coaxial fibrous delivery system, delivering approximately 20 μg/day of levonorgestrel (LNG) was used. The drug compartment is provided with crossarms fixed to the upper part of the drug delivery rod. The calculated duration of release of the system is at least 5 years. The majority of women received percutaneous 17β estradiol (Oestrogel ®, Besins Int., Belgium), 1.5 mg daily on a continuous basis, which provides sufficient blood levels of estrogen in most women to suppress climacteric symptoms and protection against bone loss. Primary outcome measures: ease of insertion, retention and side effects of the T-LNG Slim IUS. Secondary outcome measures: endometrial safety assessed by transvaginal ultrasound examination and by endometrial biopsy in a subset of women. Results: One hundred and seventy insertions were performed in postmenopausal women with median age of age 56.6 (range 43.5–80.3). Insertion was easy in 161 (94.2%) and difficult in 9 (5.3%) women. Pain at insertion was rated as none in 57 women (33.5%), mild in 105 (61.7%), moderate in 7 (4.1%) and severe in 1 (0.5%) woman. The system was well retained in the uterus as no expulsions occurred. At the time of study analysis, the total number of women-months was 1797.5. Ninety-five women had the T-LNG-IUS in place for periods in excess of 1 year. The study was well followed-up with lost-to-follow-up rate (defined as no follow-up during 12 months) of zero at the time of study analysis. The number of women continuing the method was 160 (94.1%) including four women which were released from follow-up for various non-medical related reasons. The histological examinations conducted in 105 women showed predominantly inactive endometrium characterized by a pseudo-decidual reaction of the endometrial stroma with endometrial atrophy. The mean thickness (double-layer) of the endometrium was 3.3 mm (range 2–5 mm) which correlated well with the histology results. Conclusions: The results suggest that the small T-LNG-IUS is easy to insert in most postmenopausal women without anaesthesia and dilatation of the cervix. It is well tolerated, well accepted and effective in suppressing the endometrium during EST. The lack of expulsions of the device in this study is attributed to the optimal design characteristics of the IUS, the absence of uterine bleeding and absent or reduced contractility of the uterus. The study confirms earlier studies conducted with other LNG-releasing systems used for endometrial suppression during EST. The ease of insertion of the small LNG-IUS could be an important incentive to expand the use of the continuous combined regimen with local delivery of the progestogen. It could be a method of choice for endometrial suppression in women using EST with fundamental advantages to systemically applied progestogens which have been the subject of considerable debate as reported in the recent literature.

Gross Morphology and Absorption Capacity of Cell-Fibers from the Fibrous Vascular System of Loofah (Luffa cylindrica)

This paper investigates the liquid absorbency potential of the vegetal cell-fibers (CF) of Luffa cylindrica (LC) in relation to their microscopic morphology. Absorption after drainage and centrifugation, involving deionized water and saline solutions, is measured on both the raw fibers of the vegetal net and the cell-fibers previously extracted from ligneous fibrous strands (FS) with NaOH-anthraquinone alkali treatment. The microspongy structure of the raw Fs-luffa, observed in the vegetal material by scanning electron microscopy (SEM), is formed by multicellular fibers (from 250 to 500) bonded together with a large lumen (5 to 30 μm) and containing small punctuations along the fibers as interconnections. Liquid absorption results show that this original structure of these promising fibers should contribute to good absorption capacity: 18.4g/g and 22.6g/g are respectively obtained with for broken raw FS and CF-luffa fluff treated by 5 wt % NaOH. Their absorption capacity for liquid improves with an additional formaldehyde treatment.

Design of polyvinyl alcohol mercaptyl fibers for arsenite chelation

The work described here entails the synthesis and characterization of polyvinyl alcohol mercaptyl fibers, coated on a fiberglass substrate, for the purpose of removing arsenite (As 3+) from water. Because thiols are chemically the most active functional groups found in cells and are capable of forming very stable complexes with metal ions, this functional group was selected as an excellent candidate for arsenite removal from water. The fibers were characterized through infrared spectroscopy, elemental analysis, analytical titration, scanning electron microscopy, and environmental scanning microscopy. The ability of these systems to chelate arsenite was measured using equilibrium adsorption isotherms at initial concentrations of 10 and 100 ppm. The ability to regenerate these systems is also described. The fibrous mercaptyl system’s performance is compared to the commercial product, Duolite’s GT-73, a macroreticular polystyrene–divinylbenzene resin with chelating thiol functional groups.

Developmental features of the discontinuous stem vascular system in the rattan palmCalamus(Arecaceae‐Calamoideae‐Calamineae)

Calamus is a climbing palm marked by considerable internodal extension and limited stem-thickening growth, but with a surprisingly discontinuous axial vascular system. Stem bundles end blindly in a basipetal direction and are connected to each other only by narrow and late-developing transverse commissures. Vascular connection via leaf traces between stem and leaf is made over about nine plastochrons (P), but the dominant central system is completed by about P(7), with subsequent bundles forming the crowded fibrous peripheral system, which has reduced or no vascular tissues. The stem internode below a leaf completes its extension and maturation only by P(10) to P(11). Axial stem bundles originate as procambial strands that are discontinuous apically for up to 15 plastochrons before being "captured" by a developing leaf. Their distal unconnected ends arise by dedifferentiation of ground parenchyma cells. Protoxylem is initiated as short overlapping initials that differentiate progressively during extension growth, which ruptures all but the last-formed elements. Their form, with tapered ends, means that they mature as tracheids. Metaxylem appears only late in shoot development, shortly before internodal elongation ceases (P(8)) and always unconnected to the late-differentiating protoxylem. In each axial bundle protophloem differentiates as a single strand, subsequently and much later appearing as two separate metaphloem strands as the early initials, ruptured by extension growth, are replaced by fibers. It is suggested that the unique features of this stem can be ascribed to the absence of a "meristematic cap," which otherwise typifies palms of normal habit, and that discontinuity is causally related to the pronounced late stem extension growth.

The effect on menstrual blood loss in women with uterine fibroids of a novel “frameless” intrauterine levonorgestrel-releasing drug delivery system: a pilot study

Objective: To evaluate the effect on menstrual blood loss, in women with uterine fibroids, of a novel “frameless” intrauterine drug delivery system (IUS), FibroPlant-levonorgestrel (LNG), releasing 14 μg of LNG per day. Study design: An open label, non-comparative ongoing pilot study. Fourteen insertions were performed in premenopausal women between 39 and 48 years of age for the treatment of menorrhagia. The effect on menstrual blood loss was evaluated using a simple visual assessment technique. Women were followed-up for at least 12 months (range 12–30 months). Results: At the time of study analysis the total number of women-months was 283. All women, except one reported greatly reduced bleeding. In two women, the treatment failed although both reported reduced bleeding. One failure (patient no. 4) was due to the presence of a large endometrial polyp. This patient underwent hysterectomy. The other women (patient no. 1) had submucosal fibroids. She refused hysterectomy and is continuing treatment. In the other 12 patients, reduction of bleeding was appreciable after one month of treatment and tended to decrease further over the next months to stabilize afterwards. The mean bleeding score before treatment was 465 (185–960) and dropped to a mean score of 100 (range 5–300) after a minimum of 12 months of treatment which is highly statistically significant ( P<0.001). In eight women, the bleeding reduced to very low scores. An effect on the size of the uterine fibroids could not be demonstrated. Significant spotting was rare after the first 3 months following insertion. Neither complications (e.g. infection, expulsion or perforation) nor pregnancies occurred. The FibroPlant-LNG IUS was well tolerated by all women involved in the study and no systemic hormonal side effects were reported. Conclusion: This study suggests that FibroPlant-LNG IUS is effective to significantly reduce the amount of menstrual blood loss in women with menorrhagia in the presence of intramural and subserosal fibroids and can avoid surgery. The strong endometrial suppression is the principal mechanism explaining the effect on menstrual blood loss of the IUS. The two failures probably explain that a successful treatment in women with endometrial abnormalities (e.g. polyps, submucous fibroids) is unlikely with the IUS. The low daily release rate of LNG from the FibroPlant-LNG IUS results in a low incidence of hormonal side effects. The simple design characteristics and revolutionary anchoring system account for minimizing the occurrence of complaints of pain and expulsion. The flexible fibrous delivery system adapts to cavities of every size even when severely distorted.

Cellular membranes that undergo cyclic changes in tension: Direct measurement of force generation by an in vitro contractile vacuole of Paramecium multimicronucleatum

The contractile vacuole of the fresh water protozoan Paramecium is a membrane-bound vesicle that expels excess cytosolic water, acquired osmotically, through its periodic exocytotic activity. The in vitro contractile vacuole, isolated in a small amount of cytosol from the Paramecium cell and confined under mineral oil, showed periodic rounding and slackening at regular intervals for an extended time. The contractile vacuole rounded against the cytosol-mineral oil boundary tension. The tension at the surface of the contractile vacuole is, therefore, assumed to increase during the rounding phase. We first estimated the tension relative to the boundary tension from the degree of compression of the contractile vacuole by the boundary. We then determined the absolute value for the tension at the surface of the contractile vacuole from the degree of bending of an elastic carbon fiber microcantilever (8 microm thick; 2 mm long), whose free end was placed at the surface of an in vitro contractile vacuole. The tension was found to increase to its maximum value of approximately 5 mN m(-)(1) when the contractile vacuole rounded. This value was more than 35 times higher than that for the slackened contractile vacuole. Electron micrographs of conventional thin sections of chemically fixed in vitro contractile vacuoles as well as those of in vivo contractile vacuoles obtained from rapid frozen and cryosubstituted cells revealed the lack of any ultrastructural evidence for the presence of a fibrous network system surrounding the contractile vacuole. Thus we conclude that the mechanism(s) by which tension is developed at the surface of the contractile vacuole membrane resides in the contractile vacuole membrane itself. We propose a hypothesis that periodic changes in the spontaneous curvature of the contractile vacuole's lipid bilayer membrane is involved in the periodic development of higher contractile vacuole membrane tension. The isolated CV promises to be an excellent model system for understanding the molecular mechanisms of the dynamics of biological membrane.