The Effects of Nanofiber Topography on Astrocyte Behavior and Gene Silencing Efficiency

Astrocyte‐nanofiber interactions are studied by culturing primary rat cortical astrocytes on poly[caprolactone‐co‐(ethyl ethylene phosphate)] electrospun nanofibers and solvent‐cast films (two‐dimensional control). The results indicate that nanofiber topography significantly suppresses astrocyte proliferation and enhances apoptosis, without altering cellular activation as compared to films. Moreover, nanofiber topography enhances gene‐silencing efficiency in astrocytes. The results suggest that nanofibers may serve as potential substrates for nerve regeneration by suppressing astrocyte growth and may further facilitate the use of gene‐silencing to enhance CNS regeneration.

     

Novel Biologically Inspired Collagen Nanofibers Reconstituted by Electrospinning Method

The possibility to prepare bioinspired collagen nanofibers by electrospinning from aqueous suspension of telopeptide-free collagen molecules avoiding both organic solvents and blends with any synthetic and natural polymers has been investigated. The results have highlighted the need for a basic atmosphere between the needle and the ground collector in order to increase the environmental pH during the collagen molecules self-assembly along the electrostatic force lines. Morphological, spectroscopic and calorimetric analyses carried out on the electrospun collagen nanofibers have opened the possibility to take advantage of this new approach in order to prepare an ideal biomimetic reinforcing component of new biomedical and surgical biomaterials.     

Electrospinning P(LLA-CL) Nanofiber: A Tubular Scaffold Fabrication with Circumferential Alignment

In this paper a synthetic Poly(L-lactic-co-ϵ-caprolactone) [P(LLA-CL)] (75:25) copolymer has been fabricated into a nanofibrous structure by electrospinning. The polymer crystal structure has been investigated by DSC and x-ray diffraction method. During electrospinning at room temperature, a crystallization of LLA sequence in the P(LLA-CL) copolymer could not form, while a relatively regular arrangement of CL sequence was observed. In order to obtain a tubular scaffold, a rotating mandrel was designed to collect the fiber, so that the tubular scaffold can be retrieved from the mandrel with an inner diameter same as that of the outer diameter of the mandrel. An auxiliary electrode with a sharp edge and a negative charge was set under the mandrel to guide the fiber deposition on the mandrel. When the sharp edge bar was vertical to the rotating axle of the mandrel and just beneath the spinning nozzle, nanofibers with circumferential alignment were obtained. With this method it is possible to obtain a tubular scaffold with suitable fiber alignment for blood vessel tissue engineering.     

Hybrid Scaffolds Built From PET and Collagen as a Model For Vascular Graft Architecture

A hybrid material with excellent mechanical and biological properties is produced by electrospinning a co‐solution of PET and collagen. The fibers are mapped using SEM, confocal Raman microscopy and collagenase digestion assays. Fibers of different compositions and morphologies are intermingled within the same membrane, resulting in a heterogeneous scaffold. The collagen distribution and exposure are found to depend on the PET/collagen ratio. The materials are chemically and mechanically characterized and biologically tested with fibroblasts (3T3‐L1) and a HUVEC culture in vitro. All of the hybrid scaffolds show better cell attachment and proliferation than PET. These materials are potential candidates to be used as vascular grafts.

     

Hybrid Process for Fabricating 3D Hierarchical Scaffolds Combining Rapid Prototyping and Electrospinning

An ideal scaffold should have good mechanical properties and provide a biologically functional implant site. A rapid prototyping system has been introduced as a good method of fabricating 3D scaffolds that mimic the structure in the human body. However, the scaffolds have strands that are too smooth and a pore size that is too large relative to the seeded cells and present unfavorable conditions for initial cell attachment. To overcome these problems, we propose a hybrid technology combining a 3D rapid prototyping system and an electrospinning process to produce a hierarchical 3D biomedical scaffold. The resulting structure consists of alternating layers of 3D‐structured/microsized polymer strands and nanofiber webs. The results of cell culturing of chondrocytes indicate that this technique is a feasible new method for fabricating high quality 3D polymeric scaffolds.

     

Electrospinning of hydroxypropyl methylcellulose trimellitate solutions

Nonwoven fiber mats of hydroxypropyl methylcellulose trimellitate(HPMCT) with potential applications in controlled delivery of drugs and scaffolds for tissue cultures have been successfully fabricated by electrospinning of HPMCT solutions.The formation and diameters of HPMCT fibers fabricated by electrospinning were strongly influenced by the solvents employed,electrostatic field strength,and solution concentrations.The electrospun products generated from all HPMCT solutions with various weight-average mole...     

Multi-Material Scaffolds for Tissue Engineering

A trend in developing biocompatible scaffolds for tissue engineering has been to seek an ideal single material for which a given cell type will exhibit favorable behavior. While an ideal single material has proven elusive, scaffold manufacture using combinations of specialist materials can produce more versatile structures. By controlling the percentage and architecture of material components, mechanical properties, cell attachment, and proliferation may be optimized for a given function. Three specialist materials, poly-ϵ-caprolactone (PCL), fibrin, and alginate, were incorporated into multi-component scaffolds for a series of experiments testing each component with culture of fibroblasts. The rigid and formable PCL provided structure, the fibrin pore-filler allowed for cell attachment, and alginate thread provided a nutrient transfer pathway in lieu of a vascular system. The efficacy of these scaffolds was judged on fibroblast distribution and population after 7-12 days of culture.     

Green Process to Prepare Silk Fibroin/Gelatin Biomaterial Scaffolds

A new all‐aqueous and green process is described to form three‐dimensional porous silk fibroin matrices with control of structural and morphological features. Silk‐based scaffolds are prepared using lyophilization. Gelatin is added to the aqueous silk fibroin solution to change the silk fibroin conformation and silk fibroin–water interactions through adjusting the hydrophilic interactions in silk fibroin–gelatin–water systems to restrain the formation of separate sheet like structures in the material, resulting in a more homogenous structure. Water annealing is used to generate insolubility in the silk fibroin–gelatin scaffold system, thereby avoiding the use of organic solvents such as methanol to lock in the β‐sheet structure. The adjusting of the concentration of gelatin, as well as the concentration of silk fibroin, leads to control of morphological and functional properties of the scaffolds. The scaffolds were homogeneous in terms of interconnected pores, with pore sizes ranging from 100 to 600 µm, depending on the concentration of silk fibroin used in the process. At the same time, the morphology of the scaffolds changed from lamellar sheets to porous structures based on the increase in gelatin content. Compared with salt‐leaching aqueous‐derived scaffolds and hexafluoroisopropanol (HFIP)‐derived scaffolds, these freeze‐dried scaffolds had a lower content of β‐sheet, resulting in more hydrophilic features. Most of gelatin was entrapped in the silk fibroin–gelatin scaffolds, without the burst release in PBS solution. During in vitro cell culture, these silk fibroin–gelatin scaffolds had improved cell‐compatibility than salt‐leaching silk fibroin scaffolds. This new process provides useful silk fibroin‐based scaffold systems for use in tissue engineering. Furthermore, the whole process is green, including all‐aqueous, room temperature and pressure, and without the use of toxic chemicals or solvents, offering new ways to load bioactive drugs or growth factors into the process.

     

Fabrication and Properties of Porous Collagen/Hyaluronic Composite Scaffolds Containing Nano-Bioactive Glass for Tissue Engineering

In this work, nano-structured scaffolds were designed for tissue engineering using collagen, hyaluronic acid (HA) and nano-bioactive glass (NBAG) as their main components. The scaffold was prepared via freeze-drying method and the properties including morphology, porosity, compressive strength, swelling ratio and cytotoxicity in-vitro, were also evaluated. The composite scaffolds showed well interconnected macropores with the pore size of ranging from 100 to 500 μm. The porosity percent and swelling ability were decreased with the introduction of NBAG into the collagen/HA hydrogel; however, the compressive strength was enhanced. The cytotoxicity in-vitro study shows that the collagen-HA/NBAG scaffolds have good biocompatibility with improving effect on fibroblastic cells growth. It could be concluded that this scaffold fulfills the main requirements to be considered as a bone substitute.     

Fabrication of SiO2-TiO2/PVDF Copolymer Nanofiber Composite by Electrospinning Process

Multifunctional nanocomposite material is a key material component for the future. It is indicated by many studies have been conducted by researchers in university, research institute and industries. Silicon dioxide (SiO₂), titanium dioxide (TiO₂) and polyvinilidene fluoride copolymer are very important material due to their excellent properties. In this research paper, we have successfully synthesized SiO₂-TiO₂/PVDF copolymer nanofiber composite by electrospinning process. SiO₂-TiO₂/PVDF copolymer nanofiber composite has smooth surface morphology without bead on nanofiber string after confirming by scanning electron microscopy (SEM). Nanofiber composite has average diameter of 350 nm. FTIR and XRD structure analysis of nanofiber composite show us that PVDF copolymer in nanocomposite has a mixed α and β phase crystal structure. Crystal phase of TiO₂ in nanofiber composite was in rutile form.     

Osteogenesis of Osteoblast Seeded Polyurethane-Hydroxyapatite Scaffolds in Nude Mice

Summary: Biodegradable porous polyurethane (PU) scaffolds were used in a tissue engineering approach to create new bone. Two groups of elastomeric bioresorbable PU disks were seeded with osteoblasts and implanted into nude mice. One group had disks of pure PU while the other group had disks of PU- hydroxyapatite composite (PU-HA). After 5 weeks both groups showed radiographic and histologic evidence of significant bone formation. As the new bone formed it replaced the PU scaffolds. Although not statistically significant, there was a trend toward more bone formation in the PU-HA group. Bioresorbable PU shows promise for use in bone tissue engineering.     

基于骨组织工程的静电纺纳米纤维

通过模仿天然骨的成分、结构特性对材料进行设计与调控,获得新型仿生人工骨修复材料,这已成为骨修复材料发展的主要趋势之一。静电纺纳米纤维具有可调控的纳米结构、高孔隙率和大比表面积,可以模拟天然细胞外基质的结构和生物功能,被广泛应用于骨组织工程。本文提供一个基于骨组织工程的静电纺纳米纤维的全面概述。首先简要介绍了骨组织工程,并讨论了静电纺原理、参数和典型设备。随后,讨论了静电纺纳米纤维的表面改性方法,并通过关注最具代表性的实例重点介绍了与静电纺纳米纤维和静电纺纳米纤维增强复合材料的应用最相关的最新进展。此外,本综述展望了静电纺纳米纤维未来发展的挑战、机遇以及新方向。     

Large-Scale Production of 3D Bioactive Glass Macroporous Scaffolds for Tissue Engineering

For tissue engineering applications, a scaffold is required that can act as a template and guide for cell proliferation, cell differentiation and tissue growth. Interconnected pores with diameters greater than 100 m are required for tissue ingrowth, vascularisation and nutrient delivery to the centre of the scaffold. 3D bioactive glass scaffolds have been produced, by foaming sol-gel derived bioactive glasses. The method to produce foams with a modal macropore diameter of 100 m, and a handling strength suitable for cell culture, was to foam 50 ml batches of sol with the aid of a surfactant and gelling agent. In vitro and in vivo tests show that the scaffolds have high potential to be used in bone tissue engineering applications. Larger batches are required to produce scaffolds commercially. The aim of this work was to investigate how the process could be up-scaled for commercial use. This study shows that foaming larger aliquots of sol decreased the scaffold porosity and interconnectivity and investigates methods of modifying the process to obtain large quantities of foam scaffolds with pores in excess of 100 m. The optimum method to produce foams of similar pore structure from 200 ml sol to those produced from 50 ml sol comprised of adding 3 ml surfactant and 12 ml dionised water to the sol to start foaming and injecting a gas mixture (70% helium, 30% nitrogen) at 0.2 bar while applying vigorous agitation.     

Development of Channeled Nanofibrous Scaffolds for Oriented Tissue Engineering

A tissue‐engineering scaffold resembling the structure of the natural extracellular matrix can often facilitate tissue regeneration. Nerve and tendon are oriented micro‐scale tissue bundles. In this study, a method combining injection molding and thermally induced phase separation techniques is developed to create single‐ and multiple‐channeled nanofibrous poly(L ‐lactic acid) scaffolds. The overall shape, the number and spatial arrangement of channels, the channel wall matrix architecture, the porosity and mechanical properties of the scaffolds are all tunable. The porous NF channel wall matrix provides an excellent microenvironment for protein adsorption and the attachment of PC12 neuronal cells and tendon fibroblast cells, showing potential for neural and tendon tissue regeneration.

     

Characterization on Modification and Biocompatibility of PCL Scaffold Prepared with Near-field Direct-writing Melt Electrospinning

In this study, orthogonal experiments were designed to explore the optimal process parameters for preparing polycaprolactone(PCL) scaffolds by the near-field direct-writing melt electrospinning(NFDWMES) technology. Based on the optimal process parameters, the PCL scaffolds with different thicknesses, gaps and structures were manufactured and the corresponding hydrophilicities were characterized. The PCL scaffolds were modified by chitosan (CS) and hyaluronic acid(HA) to improve biocompatibility and hydrophilicity. Both Fourier transform infrared spectroscopy(FTIR) analysis and antibacterial experimental results show that the chitosan and hyaluronic acid adhere to the surface of PCL scaffolds, sugges-ting that the modification plays a positive role in biocompatibility and antibacterial effect. The PCL scaffolds were then employed as a carrier to culture cells. The morphology and distribution of the cells observed by a fluorescence microscope demonstrate that the mo-dified PCL scaffolds have good biocompatibility, and the porous structure of the scaffolds is conducive to adhesion and deep growth of cells.     

Natural and Synthetic Polymer Scaffolds Comprising Upconversion Nanoparticles as a Bioimaging Platform for Tissue Engineering

Modern biocompatible materials of both natural and synthetic origin, in combination with advanced techniques for their processing and functionalization, provide the basis for tissue engineering constructs (TECs) for the effective replacement of specific body defects and guided tissue regeneration. Here we describe TECs fabricated using electrospinning and 3D printing techniques on a base of synthetic (polylactic-co-glycolic acids, PLGA) and natural (collagen, COL, and hyaluronic acid, HA) polymers impregnated with core/shell β-NaYF₄:Yb³⁺,Er³⁺/NaYF₄ upconversion nanoparticles (UCNPs) for in vitro control of the tissue/scaffold interaction. Polymeric structures impregnated with core/shell β-NaYF₄:Yb³⁺,Er³⁺/NaYF₄ nanoparticles were visualized with high optical contrast using laser irradiation at 976 nm. We found that the photoluminescence spectra of impregnated scaffolds differ from the spectrum of free UCNPs that could be used to control the scaffold microenvironment, polymer biodegradation, and cargo release. We proved the absence of UCNP-impregnated scaffold cytotoxicity and demonstrated their high efficiency for cell attachment, proliferation, and colonization. We also modified the COL-based scaffold fabrication technology to increase their tensile strength and structural stability within the living body. The proposed approach is a technological platform for “smart scaffold” development and fabrication based on bioresorbable polymer structures impregnated with UCNPs, providing the desired photoluminescent, biochemical, and mechanical properties for intravital visualization and monitoring of their behavior and tissue/scaffold interaction in real time.     

Wet‐Laid Meets Electrospinning: Nonwovens for Filtration Applications from Short Electrospun Polymer Nanofiber Dispersions

Dispersions of short electrospun fibers are utilized for the preparation of nanofiber nonwovens with different weight area on filter substrates. The aerosol filtration efficiencies of suspension‐borne nanofiber nonwovens are compared to nanofiber nonwovens prepared directly by electrospinning with similar weight area. The filtration efficiencies are found to be similar for both types of nonwovens. With this, a large potential opens for processing, design, and application of new nanofiber nonwovens obtained by wet‐laying of short electrospun nanofiber suspensions.

     

Micropatterned Fiber Scaffolds for Spatially Controlled Cell Adhesion

Because the local microstructure plays a pivotal role for many biological functions, a wide range of methods have been developed to design precisely engineered substrates for both fundamental biological studies and biotechnological applications. However, these techniques have been by‐and‐large limited to flat surfaces. Herein, we use electrohydrodynamic co‐spinning to prepare biodegradable three‐dimensional fiber scaffolds with precisely engineered, micrometre‐scale patterns, wherein each fiber is comprised of two distinguishable compartments. When bicompartmental fiber scaffolds are modified via spatially controlled peptide immobilization, highly selective cell guidance at spatial resolutions (<10 µm), so far exclusively reserved for flat substrates, is achieved. Microstructured fiber scaffolds may have utility for a range of biotechnological applications including tissue engineering or cell‐based assays.

     

Electrospinning of ultrafine PVDF/PC fibers from their dispersed solutions

Dispersed solutions of poly(vinylidene fluoride) (PVDF)/polycarbonate (PC) in the mixed solvent of N,N‐dimethylformamide (DMF)/tetrahydrofuran (THF) were used to electrospin in order to discuss the relationship between the properties of the polymer dispersions and the morphology of the obtained ultrafine fibers. With the changes of the mass ratio of PVDF/PC, the relative molecular mass of PVDF, and the volume ratio of DMF/THF, the morphology and the microstructure of the prepared PVDF/PC ultrafine fibers altered in accord with the viscosity, surface tension, and conductivity of the PVDF/PC dispersions. When the PVDF/PC mass ratio varied from 9/1 to 5/5, the ability of the polymer chain entanglement in PVDF/PC dispersion decreased as to the lower relative molecular mass of PC and higher chain rigidity, which lead to the formation of the beaded fibers together with the distinct core/shell structure. Similar phenomenon was also found when the lower molecular mass of PVDF was used instead of a higher one. Though the change of DMF/THF volume ratio did not specifically contribute to the properties of PVDF/PC dispersions, the accelerated evaporation and solubility of the mixed solvent by the THF amount increasing was feasible to generate the uniform fibrous morphology and the distinct core/shell structure. © 2009 Wiley Periodicals, Inc.J Polym Sci Part B: Polym Phys 48: 372–380, 2010     

Electrospinning of Chitosan

Summary: An electrospun nonwoven fabric of a cationic polysaccharide, chitosan, was successfully prepared. The present study focuses on the effect of the electrospinning solvent and the chitosan concentration on the morphology of the resulting nonwoven fabrics. The solvents tested were dilute hydrochloric acid, acetic acid, neat formic acid and trifluoroacetic acid. As the chitosan concentration was increased, the morphology of the deposition on the collector changed from spherical beads to interconnected fibrous networks. The addition of dichloromethane to the chitosan‐TFA solution improved the homogeneity of the electrospun chitosan fiber. Under optimized conditions, homogenous (not interconnected) chitosan fibers with a mean diameter of 330 nm were prepared.

Effects of the coexisting dichloromethane (MC) in the prespun chitosan‐TFA solution on the morphology of the electrospun chitosan fibers. The volume ratio of TFA:MC was 70:30 (×5 000).