3D Fibrous Structure Research Articles

Low Molecular Weight Gelators Bearing Electroactive Groups as Cathode Materials for Rechargeable Batteries

SummaryLow molecular weight gelators bearing 2,2,6,6‐tetramethyl‐piperidine‐1‐oxyl (TEMPO) were synthesized and demonstrated to have reversible electrochemical redox properties. The gelation tests showed that the compounds have excellent gelation properties in γ‐butyrolactone and propylene carbonate. Atomic force microscopy and transmission electron microscopy images showed the 3D network fibrous structure with an average diameter of 20–50 nm. Fast and reversible charge storage capabilities were established for the gelators, with an average output voltage of 4.8 V.

Low-Molecular-Weight Organo- and Hydrogelators Based on Cyclo(l-Lys-l-Glu).

Four cyclo(l-Lys-l-Glu) derivatives (3-6) were synthesized from the coupling reaction of protecting l-lysine with l-glutamic acid followed by the cyclization, deprotection, and protection reactions. They can efficiently gelate a wide variety of organic solvents or water. Interestingly, a spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting not only visual color alteration but also increasing mechanical strength with the progress of time due to the formation of Schiff base. Moreover, 6 bearing a carboxylic acid and Fmoc group displayed a robust hydrogelation capability in PBS solution. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the characteristic gelation morphologies of 3D fibrous network structures in the resulting organo- and hydrogels. FT-IR and fluorescence analyses indicated that the hydrogen bonding and π-π stacking play as major driving forces for the self-assembly of these cyclic dipeptides as low-molecular-weight gelators. X-ray diffraction (XRD) measurements and computer modeling provided information on the molecular packing model in the hydrogelation state of 6. A spontaneous chemical reaction proceeded in the organogel obtained from 3 in acetone exhibiting visual color alteration and increasing mechanical strength. 6 bearing an optimized balance of hydrophilicity to lipophilicity gave rise to a hydrogel in PBS with MGC at 1 mg/mL.

Confluent 3D-assembly of fibrous structures

The ability to independently control fiber alignments and structural geometry is critical for design of optimal three-dimensional (3D) fibrous structures. We present a novel method to 3D-assemble carbon fiber structures, containing no seams or adhesive joints, using a confluence of several textile methodologies. A variety of complex structural shapes with tailored fiber topologies are demonstrated to be achievable. These optimized structures are shown to have unprecedented static and dynamic strength as well as damage tolerance and ductility. For example, the energy absorption capacity of a 3D-assembled carbon fiber prismatic sandwich structure is shown to be 300% greater than a high performance metallic counterpart.

Bacterial cellulose composites: Synthetic strategies and multiple applications in bio-medical and electro-conductive fields.

Bacterial cellulose (BC), owing to its pure nature and impressive physicochemical properties, including high mechanical strength, crystallinity, porous fibrous structure, and liquid absorbing capabilities, has emerged as an advanced biomaterial. To match the market demand and economic values, BC has been produced through a number of synthetic routes, leading to slightly different structural features and physical appearance. Chemical nature, porous geometry, and 3D fibrous structure of BC make it an ideal material for composites synthesis that successfully overcome certain deficiencies of pure BC. In this review, we have focused various strategies developed for synthesizing BC and BC composites. Reinforcement materials including nanoparticles and polymers have enhanced the antimicrobial, conducting, magnetic, biocompatible, and mechanical properties of BC. Both pure BC and its composites have shown impressive applications in medical fields and in the development of optoelectronic devices. Herein, we have given a special attention to discuss its applications in the medical and electronic fields. In conclusion, BC and BC composites have realistic potential to be used in future development of medical devices, artificial organs and electronic and conducting materials. The contents discussed herein will provide an eye-catching theme to the researchers concerned with practical applications of BC and BC composites.

3D multi-layered fibrous cellulose structure using an electrohydrodynamic process for tissue engineering

Micro/nanofibrous structures have been applied widely in various tissue-engineering applications because the topological structures are similar to the extracellular matrix (ECM), which encourages a high degree of cell adhesion and growth. However, it has been difficult to produce a three-dimensional (3D) fibrous structure using controllable macro-pores. Recently, cellulose has been considered a high-potential natural-origin biomaterial, but its use in 3D biomedical structures has been limited due to its narrow processing window. Here, we suggest a new 3D cellulose scaffold consisting of multi-layered struts made of submicron-sized entangled fibers that were fabricated using an electrohydrodynamic direct jet (EHDJ) process that is spin-printing. By optimizing processing conditions (electric field strength, cellulose feeding rate, and distance between nozzle and target), we can achieve a multi-layered cellulose structure consisting of the cylindrically entangled cellulose fibers. To compare the properties of the fabricated 3D cellulose structure, we used a PCL fibrous scaffold, which has a similar fibrous morphology and pore geometry, as a control. The physical and in vitro biocompatibilities of both fibrous scaffolds were assessed using human dermal fibroblasts, and the cellulose structure showed higher cell adhesion and metabolic activities compared with the control. These results suggest the EHDJ process to be an effective fabricating tool for tissue engineering and the cellulose scaffold has high potential as a tissue regenerative material.

Optimization of fibrous structures with cellulose fibres, polyacrylamide polymers and CaCO3 fillers: Experimental characterization for computational simulation

In the development and optimization of advanced fibrous materials, it is very important to design a material with a certain structure, and also with the ability to retain in the fibre network of other non‐fibrous materials. In this work the experimental characterization and optimization of 3D cellulose fibre structures containing an inorganic filler is presented. The cellulose fibres were chosen from to different wood species, Eucalyptus globulus and Picea abies, to have different representative fibre dimensions, and the selected inorganic filler was precipitated calcium carbonate (PCC). For the incorporation of precipitated calcium carbonate in the cellulosic fibre network four different types of polyacrylamide (Pam) were used as polymeric 3D retention agents. Pam B was identified as being the most effective with an incorporation of 15.3%, three times the incorporation obtained without Pam. The precipitated calcium carbonate retained in the 3D fibrous structure is determined by incineration. The fibrous structures were simulated using a computational simulator validated for fibrous materials to obtain information about the porosity and structure of the fibrous network without precipitated calcium carbonate.

Mesoporous silica-layered biopolymer hybrid nanofibrous scaffold: a novel nanobiomatrix platform for therapeutics delivery and bone regeneration.

Nanoscale scaffolds that characterize high bioactivity and the ability to deliver biomolecules provide a 3D microenvironment that controls and stimulates desired cellular responses and subsequent tissue reaction. Herein novel nanofibrous hybrid scaffolds of polycaprolactone shelled with mesoporous silica (PCL@MS) were developed. In this hybrid system, the silica shell provides an active biointerface, while the 3D nanoscale fibrous structure provides cell-stimulating matrix cues suitable for bone regeneration. The electrospun PCL nanofibers were coated with MS at controlled thicknesses via a sol-gel approach. The MS shell improved surface wettability and ionic reactions, involving substantial formation of bone-like mineral apatite in body-simulated medium. The MS-layered hybrid nanofibers showed a significant improvement in mechanical properties, in terms of both tensile strength and elastic modulus, as well as in nanomechanical surface behavior, which is favorable for hard tissue repair. Attachment, growth, and proliferation of rat mesenchymal stem cells were significantly improved on the hybrid scaffolds, and their osteogenic differentiation and subsequent mineralization were highly up-regulated by the hybrid scaffolds. Furthermore, the mesoporous surface of the hybrid scaffolds enabled the loading of a series of bioactive molecules, including small drugs and proteins at high levels. The release of these molecules was sustainable over a long-term period, indicating the capability of the hybrid scaffolds to deliver therapeutic molecules. Taken together, the multifunctional hybrid nanofibrous scaffolds are considered to be promising therapeutic platforms for stimulating stem cells and for the repair and regeneration of bone.

Microstructural parameter-based modeling for transport properties of collagen matrices.

Recent advances in modulating collagen building blocks enable the design and control of the microstructure and functional properties of collagen matrices for tissue engineering and regenerative medicine. However, this is typically achieved by iterative experimentations and that process can be substantially shortened by computational predictions. Computational efforts to correlate the microstructure of fibrous and/or nonfibrous scaffolds to their functionality such as mechanical or transport properties have been reported, but the predictability is still significantly limited due to the intrinsic complexity of fibrous/nonfibrous networks. In this study, a new computational method is developed to predict two transport properties, permeability and diffusivity, based on a microstructural parameter, the specific number of interfibril branching points (or branching points). This method consists of the reconstruction of a three-dimensional (3D) fibrous matrix structure based on branching points and the computation of fluid velocity and solute displacement to predict permeability and diffusivity. The computational results are compared with experimental measurements of collagen gels. The computed permeability was slightly lower than the measured experimental values, but diffusivity agreed well. The results are further discussed by comparing them with empirical correlations in the literature for the implication for predictive engineering of collagen matrices for tissue engineering applications.

Bio-inspired fabrication of hierarchical Ni-Fe-P coated skin collagen fibers for high-performance microwave absorption.

In the present investigation, skin collagen fiber (CF) with a well defined hierarchical 3D fibrous structure was employed for the bio-inspired fabrication of high-performance microwave absorption materials. The hierarchical 3D structure of the CF was retained in the CF@Ni-Fe-P composites, and the formation of the Ni-Fe-P coating on the CF surface was identified by XRD and XPS analysis. Based on the electromagnetism parameter measurements, the maximum reflection loss (RL) of the CF@Ni-Fe-P composites reached -31.0 dB, and the width of the absorption band where reflection loss values exceeded -10.0 dB covered the whole Ku-band and some parts of the X-band (9.5-18.0 GHz). The complex permittivity and complex permeability measurements indicated that electronic loss and magnetic loss were involved in the CF@Ni-Fe-P composites for microwave absorption. In addition, due to the magnetic properties of the Ni-Fe-P coating, these CF@Ni-Fe-P composites exhibited excellent magnetic characteristics with high saturation magnetization and low coercivity values. The present investigation indicates a new possibility for the bio-matrix-based fabrication of high-performance microwave absorbing materials with lightweight and efficient absorption properties.

Electrohydrodynamic jet process for pore-structure-controlled 3D fibrous architecture as a tissue regenerative material: fabrication and cellular activities.

In this study, we propose a new scaffold fabrication method, "direct electro-hydrodynamic jet process," using the initial jet of an electrospinning process and ethanol media as a target. The fabricated three-dimensional (3D) fibrous structure was configured with multilayered microsized struts consisting of randomly entangled micro/nanofibrous architecture, similar to that of native extracellular matrixes. The fabrication of the structure was highly dependent on various processing parameters, such as the surface tension of the target media, and the flow rate and weight fraction of the polymer solution. As a tissue regenerative material, the 3D fibrous scaffold was cultured with preosteoblasts to observe the initial cellular activities in comparison with a solid-freeform fabricated 3D scaffold sharing a similar structural geometry. The cell-culture results showed that the newly developed scaffold provided outstanding microcellular environmental conditions to the seeded cells (about 3.5-fold better initial cell attachment and 2.1-fold better cell proliferation).

Intrinsically water-stable electrospun three-dimensional ultrafine fibrous soy protein scaffolds for soft tissue engineering using adipose derived mesenchymal stem cells

Soy protein, the plant protein from soybean, was electrospun into intrinsically water-stable scaffolds with large volume and ultrafine fibers oriented randomly and evenly in three dimensions (3D) to simulate native extracellular matrices of soft tissues. The 3D ultrafine fibrous scaffolds from proteins could be favored in soft tissue engineering. However, protein-based biomaterials usually suffered from poor water stability, while the highly crosslinked proteins which had water stability were usually difficult to be fabricated into fibers. Soy protein was a typical protein with intrinsic water stability, attributed to its 1.2% cysteine content. Soy protein has been developed into 3D non-fibrous structures, coarse fibers and films for tissue engineering applications, but not ultrafine fibrous structures. In this research, the disulfide crosslinks in soy protein were cleaved to facilitate its dissolution in an aqueous solvent system. The obtained solution was electrospun into bulky scaffolds composed of ultrafine fibers oriented randomly in three dimensions. Without external crosslinking, the fibrous soy protein scaffolds demonstrated long-term water stability, and maintained their fibrous structures after incubated in PBS for up to 28 days. In vitro study showed that the 3D soy protein scaffolds well supported uniform distribution and adipogenic differentiation of adipose derived mesenchymal stem cells. In summary, the 3D ultrafine fibrous soy protein structures could be good candidates as scaffolds in soft tissue engineering.

Physical and compressional characteristics of a novel 3D fibrous structure – application in comparison between PU foam and 3D fibrous structure

The question of the recycling of the polyurethane (PU) foam, especially in the automotive industry represents one of the main technology thrust and challenge of the car manufacturers and the Original Equipment Manufacturers’ (OEM) since 2000. Indeed, it is nowadays necessary for car industry to promote ecological methods of development in regard to new consumer sensibility. New textile products present the best alternative solutions to answer this issue of replacement of the PU foam. Based on this fact, a new three-dimensional (3D) fibrous structure made of polyester (PET) material has been developed in order to replace PU foam in automotive trim. These new manufactured 3D fibrous structures are laminated with needle-punched and spun-bonded sheets. The sheets are made of 100% PET, in order to obtain a mono component product. Characterization of physical and mechanical properties of these new 3D fibrous structures, testing methods have to be developed. Based on the automotive specifications, a methodology has been set up to test the compression behavior of these new products. In order to answer the issue of replacement, some PU foam products have also been characterized, and comparisons with alternative products have been conducted. The results of this study show interesting properties of the new 3D fibrous structure in terms of compression behavior when compared to the PU foam.

Highly porous 3D nanofibrous scaffolds processed with an electrospinning/laser process

Electrospinning has been widely used to produce micro/nanosized fibres. Although the method is very simple, easy, and effective for obtaining nanosized material, the fabrication of three dimensional (3D) shapes comprised of micro/nanofibres has been a major obstacle for use in tissue engineering. In this study, a new electrospinning method to fabricate controllable 3D micro/nanofibrous structure (with thickness over 3 mm) is suggested. The fabricated 3D fibrous structure was fully porous and successfully consisted of submicron-sized fibres. However, the pores in the 3D fibrous structure were too small (5–10 μm), so we used a femtosecond laser process to achieve enough cell infiltration and proliferation in the thickness direction of the 3D structure. By controlling appropriate processing conditions, we can successfully fabricate a highly porous 3D micro/nanofibrous structure with various pore sizes ranging from 189 ± 28 μm to 380 ± 21 μm. The fabricated 3D fibrous scaffolds were assessed for in vitro biological capabilities by culturing osteoblast like cells (MG63). Compared with the rapid-prototyped PCL scaffold, the 3D fibrous scaffold exhibited significantly higher biological activities (initial cell attachment and cell proliferation) due to the topographical structure of micro/nanofibres.

Physical and mechanical characterizations of recyclable insole product based on new 3D textile structure developed by the use of a patented vertical-lapping process

This paper deals with physical properties and compression behavior of new insole structure. This insole is developed based on a new 3D fibrous structure made of recycled polyester nonwoven (110 g/cm2) laminated with different textile materials by the use of a patented vertical-lapping process (VERTILAP®). To characterize physical and mechanical properties of the 3D structures, a methodology has been set up and new testing methods have been developed. The results of this study have shown interesting properties in terms of comfort and compression behavior (under static and dynamic loading). It has been observed that the 3D structure laminated with hemp woven fabric has the highest water absorbency, the highest thermal conductivity and the coolest touch effect compared to nonwoven made of a blend of polyester and viscose fibers. The compression behavior of the insole has been influenced by the physical properties of the 3D structure. The insoles developed in this work have a viscoelastic behavior with cushioning properties and can resist up to 218 kPa at 50% of deformation under static compression conditions and dissipate sufficient energy (higher than 180 N.mm) which allows the relieve of the foot pressure and distributes loads more evenly on the soft parts of the feet in use case.

A new tetraarylcyclopentadienone based low molecular weight gelator: synthesis, self-assembly properties and anion recognition

A new class of tetraarylcyclopentadienones bearing 3-hydroxy-1-propynyl substituents has been synthesized. One of them, 3,4-bis (4-(3-hydroxy-3-methylbut-1-ynyl) phenyl)-2,5-diphenylcyclopenta-2,4-dienone, exhibits pronounced aggregation properties in various organic solvents responding to thermal and ultrasound stimuli and represents the first example of a tetraarylcyclopentadienone based low molecular weight organogelator. The hydroxydimethyl group on the ethynyl substituent proved to be essential to perform the gelation process. The 1H NMR analysis and FT-IR spectroscopy suggested that the intermolecular π–π and hydrogen bonding interactions of the gelator with the solvent are the main driving forces for the supramolecular assembly. The SEM images of xerogels show the characteristic gelation morphologies of 3D fibrous network structures. Fluorescence and UV/Vis absorption studies provided more information to define the molecular packing model in the gelation state. In addition the obtained gels show selective response to the fluoride anion.

Anion influenced self-assembly of stilbazolium derivative and acid-sensitive property of its corresponding gel

Two stilbazolium derivatives with different counter-anions (Br− and OH− ) have been designed and synthesised. Different counter-anions cause different aggregation properties. The reason of this difference was investigated through concentration- and temperature-dependent 1H NMR and IR spectra. When the counter-anion is OH− , the stilbazolium derivative exhibits pronounced aggregation properties. The scanning electron microscope images of xerogels show the characteristic gelation morphologies of 3D fibrous network structures. X-ray diffraction and fluorescence spectroscopy studies have been carried out, and provide more information to define the molecular packing model in gelation states. Finally, the acid-sensing abilities of the xerogel film were studied.

Novel three‐dimensional scaffolds of poly(L‐lactic acid) microfibers using electrospinning and mechanical expansion: Fabrication and bone regeneration

Poly(L-lactic acid) (PLLA) microfibrous scaffolds with three-dimensional (3D) structures were fabricated using an electrospinning technique with a subsequent mechanical expansion process. To achieve a 3D fibrous structure, the fusion at the contact points of the as-spun PLLA microfibers was avoided using an appropriate binary solvent system of methylene chloride and acetone. The solvent composition was optimized based on the solvent power, volatility, and viscosity (methylene chloride:acetone = 9:1 volume ratio). The final 3D structure of the electrospun scaffolds was obtained after mechanical expansion of the electrospun microfibrous mats. The pore sizes of the scaffolds were controlled by varying the degree of expansion of the nonbonded microfibrous mats, and they were in the range of several microns up to 400 μm. The 3D scaffolds were examined for their morphological properties and their potential use for the proliferation of osteoblasts. Generally recognized electrospun 2D nanofibrous membranes were also tested in order to compare the cell behaviors using different scaffold geometries. The 3D scaffolds demonstrated a high level of osteoblast proliferation (1.8-fold higher than nanofibrous membranes in a week). The osteoblasts actively penetrated the inside of the 3D scaffold and showed a spatial cell distribution, as confirmed by SEM and H&E staining, while a monolayer formed in the case of the 2D nanofibrous membranes with limited cell infiltration. In vivo results further showed that 3D electrospun microfibrous matrices were a favorable substrate for cell infiltration and bone formation after 2 and 4 weeks, using a rabbit calvarial defect model. In this study, the 3D microfibrous PLLA scaffolds fabricated using electrospinning techniques might be an innovative addition to tissue engineering applications.

Novel Urea‐Functionalized Quinacridone Derivatives: Ultrasound and Thermo Effects on Supramolecular Organogels

In investigations into the effects of environmental factors on organogels, two urea-functionalized quinacridone derivatives 1a and 1b have been designed and synthesized. These two compounds can respond to ultrasound and thermal stimuli in the organic test solvents, and exhibit pronounced aggregation properties. The field-effect (FE)-SEM images of xerogels show the characteristic gelation morphologies of 3D fibrous network structures. The concentration- and temperature-dependent (1)H NMR spectra suggest that the intermolecular π-π and hydrogen-bonding interactions of gelators are the main driving forces for the supramolecular assembly process. X-ray diffraction (XRD), UV/Vis absorption, and photoluminescent spectroscopy studies have been carried out and provide more information to define the molecular packing model in gelation states.

Electrospun nanofibers: Work for medicine?

Attempts have been made to fabricate nanofibrous scaffolds to mimic the chemical composition and structural properties of the extracellular matrix (ECM) for tissue/organ replacement. Nanofiber scaffolds with various patterns have been successfully produced from synthetic and natural polymers through a relatively simple technique of electrospinning. The resulting patterns can mimic some of the diverse tissue-specific orientation and three-dimensional (3D) fibrous structures. Studies on cell-nanofiber interactions, including studies on stem cells, have revealed the importance of nanotopography on cell adhesion, proliferation and differentiation. Furthermore, clinical application of electrospun nanofibers including wound healing, tissue regeneration, drug delivery and stem cell therapy are highly feasible due to the ease and flexibility of fabrication of making nanofiber with this cost-effective method using electrospinning. In this review, we have highlighted the current state of the art and provided future perspectives on electrospun nanofiber in medical applications.

Imaging of Cell-to-Material Interfaces by SEM after in situ Focused Ion Beam Milling on Flat Surfaces and Complex 3D-Fibrous Structures

Detailed analysis of the cell-to-implant interface needs to be performed prior to medical application. As these interfaces are often not accessible for direct visualization SEM after in situ focused ion beam milling was explored that allows selecting the regions of interest and serial sectioning for analysis of large scale implant architecture/topology down to detailed sub-cellular structures in one sample that might be very useful for (bio)material characterization.