3D Fibrous Scaffolds Research Articles

Electric-field assisted 3D-fibrous bioceramic-based scaffolds for bone tissue regeneration: Fabrication, characterization, and in vitro cellular activities

Nano/microfibrous structure can induce high cellular activities because of the topological similarity of the extracellular matrix, and thus, are widely used in various tissue regenerative materials. However, the fabrication of a bioceramic (high weight percent)-based 3D microfibrous structure is extremely difficult because of the low process-ability of bioceramics. In addition, three-dimensional (3D) microfibrous structure can induce more realistic cellular behavior when compared to that of 2D fibrous structure. Hence, the requirement of a 3D fibrous ceramic-based structure is an important issue in bioceramic scaffolds. In this study, a bioceramic (α-TCP)-based scaffold in which the weight fraction of the ceramic exceeded 70% was fabricated using an electrohydrodynamic printing (EHDP) process. The fabricated ceramic structure consisted of layer-by-layered struts entangled with polycaprolactone microfibers and the bioceramic phase. Various processing conditions (such as applied electric field, flow rate, nozzle size, and weight fraction of the bioceramic) were manipulated to obtain an optimal processing window. A 3D printed porous structure was used as a control, which had pore geometry similar to that of a structure fabricated using the EHDP process. Various physical and cellular activities using preosteoblasts (MC3T3-E1) helped confirm that the newly designed bioceramic scaffold demonstrated significantly high metabolic activity and mineralization.

Design of a novel electrospinning setup for the fabrication of biomimetic scaffolds for meniscus tissue engineering applications

The tissue engineering field has provided great efforts towards the development of potential treatments for meniscal injuries. The success of these strategies are linked to the creation of scaffolds that are able to mimic the extracellular matrix architecture of the native meniscus. However, most conventional electrospinning setups can only produce either 2D aligned fibrous structures or 3D fibrous scaffolds with fibers randomly distributed. Herein, we designed a novel electrospinning setup, which consisted of two metallic devices as collectors: an external cylindrical hollow piece with a central pin and a mobile internal hollow cylinder. A feasible approach to create single-layer scaffolds with both circumferentially and radially aligned ultrathin fibers was developed. Then, this investigation demonstrated a great potential for the application of these scaffolds towards meniscus tissue engineering, once they are able to reproduce the orientation of the main collagen fibers present in the extracellular matrix of the knee meniscus.

Platelet-functionalized three-dimensional poly-ε-caprolactone fibrous scaffold prepared using centrifugal spinning for delivery of growth factors

Bone and cartilage are tissues of a three-dimensional (3D) nature. Therefore, scaffolds for their regeneration should support cell infiltration and growth in all 3 dimensions. To fulfill such a requirement, the materials should possess large, open pores. Centrifugal spinning is a simple method for producing 3D fibrous scaffolds with large and interconnected pores. However, the process of bone regeneration is rather complex and requires additional stimulation by active molecules. In the current study, we introduced a simple composite scaffold based on platelet adhesion to poly-ε-caprolactone 3D fibers. Platelets were used as a natural source of growth factors and cytokines active in the tissue repair process. By immobilization in the fibrous scaffolds, their bioavailability was prolonged. The biological evaluation of the proposed system in the MG-63 model showed improved metabolic activity, proliferation and alkaline phosphatase activity in comparison to nonfunctionalized fibrous scaffold. In addition, the response of cells was dose dependent with improved biocompatibility with increasing platelet concentration. The results demonstrated the suitability of the system for bone tissue.

Cell infiltrative hydrogel fibrous scaffolds for accelerated wound healing.

In present study, we generate three-dimensional photocrosslinkable gelatin (GelMA)-based fibrous scaffolds with tunable physical and biological properties by using a combined photocrosslinking/electrospinning approach. The developed GelMA fibrous scaffolds can not only support cell viability and cell adhesion, but also facilitate cell migration and proliferation, accelerating regeneration and formation of cutaneous tissues. In addition, the physical properties of the engineered fibrous GelMA hydrogel including water retention capability, mechanical properties and biodegradability can be tuned to accommodate different patients' needs, making it a promising candidate for skin tissue engineering.

Electrospun Photocrosslinkable Hydrogel Fibrous Scaffolds for Rapid In Vivo Vascularized Skin Flap Regeneration

Distal necrosis of random skin flap is always clinical problematic in plastic surgery. The development of 3D functional vascular networks is fundamental for the survival of a local random skin flap. Herein, an effective technique on constructing 3D fibrous scaffolds for accelerated vascularization is demonstrated using a photocrosslinkable natural hydrogel based on gelatin methacryloyl (GelMA) by electrospinning. It is found that the ultraviolet (UV) photocrosslinkable gelatin electrospun hydrogel fibrous membranes exhibit soft adjustable mechanical properties and controllable degradation properties. Furthermore, it is observed that the optimized hydrogel scaffolds can support endothelial cells and dermal fibroblasts adhesion, proliferation, and migration into the scaffolds, which facilitates vascularization. Importantly, a rapid formation of tubes is observed after 3 d seeding of endothelial cells. After GelMA fibrous scaffold implantation below the skin flap in a rat model, it is found that the flap survival rate is higher than the control group, and there is more microvascular formation, which is potentially beneficial for the flap tissue vascularization. These data suggest that GelMA hydrogels can be used for biomedical applications that require the formation of microvascular networks, including the development of complex engineered tissues.

Exceptional biocompatibility of 3D fibrous scaffold for cardiac tissue engineering fabricated from biodegradable polyurethane blended with cellulose

ABSTRACTThe auhtors report 3D biomimetic scaffolds using polymer blend of polyurethane and cellulose for cardiac tissue engineering. The biocompatible and biodegradable polyurethane is designed, synthesized and characterized. By incorporating 10 wt% of naturally ordered cellulose into the polyurethane and electrospinning them into 3D scaffold, the scaffold exhibits good biocompatibility and mechanical property to support and accommodate constant cycles of contraction/expansion of cardiac tissue. The biocompatibility is further improved using scaffold fabricated from aligned fibers due to synergistic effects between cells and ordered macromolecules. The anisotropic structured scaffold is mimicked the extracellular matrix and has therapeutic potential in reconstruction of damaged myocardium.

Additive manufactured polymeric 3D scaffolds with tailored surface topography influence mesenchymal stromal cells activity

Additive manufactured three-dimensional (3D) scaffolds with tailored surface topography constitute a clear advantage in tissue regeneration strategies to steer cell behavior. 3D fibrous scaffolds of poly(ethylene oxide terephthalate)/poly(butylene terephthalate) block copolymer presenting different fiber surface features were successfully fabricated by additive manufacturing combined with wet-spinning, in a single step, without any post-processing. The optimization of the processing parameters, mainly driven by different solvent/non-solvent combinations, led to four distinct scaffold types, with average surface roughness values ranging from 0.071 ± 0.012 μm to 1.950 ± 0.553 μm, average pore sizes in the x- and y-axis between 351.1 ± 33.6 μm and 396.1 ± 32.3 μm, in the z-axis between 36.5 ± 5.3 μm and 70.7 ± 8.8 μm, average fiber diameters between 69.4 ± 6.1 μm and 99.0 ± 9.4 μm, and porosity values ranging from 60.2 ± 0.8% to 71.7 ± 2.6%. Human mesenchymal stromal cells (hMSCs) cultured on these scaffolds adhered, proliferated, and produced endogenous extracellular matrix. The effect of surface roughness and topography on hMSCs differentiation was more evident for cells seeded at lower density, where the percentage of cells in direct contact with the surface was higher compared to more densely seeded scaffolds. Under osteogenic conditions, lower surface roughness values (0.227 ± 0.035 μm) had a synergistic effect on hMSCs behavior, while chondrogenesis was favored on rougher surfaces (1.950 ± 0.553 μm).

Mechanically-enhanced three-dimensional scaffold with anisotropic morphology for tendon regeneration.

Tissue engineering has showed promising results in restoring diseased tendon tissue functions. Herein, a hybrid three-dimensional (3D) porous scaffold comprising an outer portion rolled from an electrohydrodynamic jet printed poly(ɛ-caprolactone) (PCL) fiber mesh, and an inner portion fabricated from uniaxial stretching of a heat-sealed PCL tube, was developed for tendon tissue engineering (TE) application. The outer portion included three layers of micrometer-scale fibrous bundles (fiber diameter: ~25µm), with an interconnected spacing and geometric anisotropy along the scaffold length. The inner portion showed orientated micro-ridges/grooves in a parallel direction to that of the outer portion. Owning to the addition of the inner portion, the as-fabricated scaffold exhibited comparable mechanical properties to those of the human patellar tendon in terms of Young's modulus (~227MPa) and ultimate tensile stress (~50MPa). Compared to the rolled electrospun fibers, human tenocytes cultured in the tendon scaffolds showed increased cellular metabolism. Furthermore, the 3D tendon scaffold resulted in up-regulated cell alignment, cell elongation and formation of collagen type I. These results demonstrated the potential of mechanically-enhanced 3D fibrous scaffold for applications in tendon TE, with desired cell alignment and functional differentiation.

Preparation and properties of a magnetic field responsive three-dimensional electrospun polymer scaffold

Abstract In tissue engineering a permeable 3D fibrous macrostructure with high surface area is desired for cell attachment and growth. In this paper novel experimental technique is reported to prepare 2D and 3D fibrous scaffolds by reactive electrospinning as a potential matrix for cell culturing. The sub-micrometer sized fibrous scaffolds were synthesized from chemically cross-linked poly(succinimide) molecules (anhydrous form of poly(aspartic acid)). Magnetically active particles of what the size distribution was determined by small- and wide angle X-ray scattering were incorporated into the fibers. The morphology of loaded and unloaded fibers was studied by light- and atomic force microscopy. It was found that coupling elastic and magnetic properties within the 3D flexible scaffold enables continuous non-contact mode of mechanical agitation by external magnetic field. These unique properties can be exploited in cell culturing or in magnetic hyperthermia in solid-like matrix.

Electrospun 3D Fibrous Scaffolds for Chronic Wound Repair.

Chronic wounds are difficult to heal spontaneously largely due to the corrupted extracellular matrix (ECM) where cell ingrowth is obstructed. Thus, the objective of this study was to develop a three-dimensional (3D) biodegradable scaffold mimicking native ECM to replace the missing or dysfunctional ECM, which may be an essential strategy for wound healing. The 3D fibrous scaffolds of poly(lactic acid-co-glycolic acid) (PLGA) were successfully fabricated by liquid-collecting electrospinning, with 5~20 µm interconnected pores. Surface modification with the native ECM component aims at providing biological recognition for cell growth. Human dermal fibroblasts (HDFs) successfully infiltrated into scaffolds at a depth of ~1400 µm after seven days of culturing, and showed significant progressive proliferation on scaffolds immobilized with collagen type I. In vivo models showed that chronic wounds treated with scaffolds had a faster healing rate. These results indicate that the 3D fibrous scaffolds may be a potential wound dressing for chronic wound repair.

Direct E-jet printing of three-dimensional fibrous scaffold for tendon tissue engineering.

Tissue engineering (TE) offers a promising strategy to restore diseased tendon tissue. However, a suitable scaffold for tendon TE has not been achieved with current fabrication techniques. Herein, we report the development of a novel electrohydrodynamic jet printing (E-jetting) for engineering 3D tendon scaffold with high porosity and orientated micrometer-size fibers. The E-jetted scaffold comprised tubular multilayered micrometer-size fibrous bundles, with interconnected spacing and geometric anisotropy along the longitudinal direction of the scaffold. Fiber diameter, stacking pattern, and interfiber distance have been observed to affect the structural stability of the scaffold, of which the enhanced mechanical strength can be obtained for scaffolds with thick fibers as the supporting layer. Human tenocytes showed a significant increase in cellular metabolism on the E-jetted scaffolds as compared to that on conventional electrospun scaffolds (2.7-, 2.8-, and 3.1-fold increase for 150, 300, and 600 µm interfiber distance, respectively; p < 0.05). Furthermore, the scaffolds provided structural support for human tenocytes to align with controlled orientation along the longitudinal direction of the scaffold, and promoted the expression of collagen type I. For the first time, E-jetting has been explored as a novel scaffolding approach for tendon TE, and offers a 3D fibrous scaffold to promote organized tissue reconstruction for potential tendon healing. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 616-627, 2017.

Adapting the Electrospinning Process to Provide Three Unique Environments for a Tri-layered In Vitro Model of the Airway Wall.

Electrospinning is a highly adaptable method producing porous 3D fibrous scaffolds that can be exploited in in vitro cell culture. Alterations to intrinsic parameters within the process allow a high degree of control over scaffold characteristics including fiber diameter, alignment and porosity. By developing scaffolds with similar dimensions and topographies to organ- or tissue-specific extracellular matrices (ECM), micro-environments representative to those that cells are exposed to in situ can be created. The airway bronchiole wall, comprised of three main micro-environments, was selected as a model tissue. Using decellularized airway ECM as a guide, we electrospun the non-degradable polymer, polyethylene terephthalate (PET), by three different protocols to produce three individual electrospun scaffolds optimized for epithelial, fibroblast or smooth muscle cell-culture. Using a commercially available bioreactor system, we stably co-cultured the three cell-types to provide an in vitro model of the airway wall over an extended time period.This model highlights the potential for such methods being employed in in vitro diagnostic studies investigating important inter-cellular cross-talk mechanisms or assessing novel pharmaceutical targets, by providing a relevant platform to allow the culture of fully differentiated adult cells within 3D, tissue-specific environments.

Adapting the Electrospinning Process to Provide Three Unique Environments for a Tri-layered &lt;em&gt;In Vitro&lt;/em&gt; Model of the Airway Wall

Electrospinning is a highly adaptable method producing porous 3D fibrous scaffolds that can be exploited in in vitro cell culture. Alterations to intrinsic parameters within the process allow a high degree of control over scaffold characteristics including fiber diameter, alignment and porosity. By developing scaffolds with similar dimensions and topographies to organ- or tissue-specific extracellular matrices (ECM), micro-environments representative to those that cells are exposed to in situ can be created. The airway bronchiole wall, comprised of three main micro-environments, was selected as a model tissue. Using decellularized airway ECM as a guide, we electrospun the non-degradable polymer, polyethylene terephthalate (PET), by three different protocols to produce three individual electrospun scaffolds optimized for epithelial, fibroblast or smooth muscle cell-culture. Using a commercially available bioreactor system, we stably co-cultured the three cell-types to provide an in vitro model of the airway wall over an extended time period. This model highlights the potential for such methods being employed in in vitro diagnostic studies investigating important inter-cellular cross-talk mechanisms or assessing novel pharmaceutical targets, by providing a relevant platform to allow the culture of fully differentiated adult cells within 3D, tissue-specific environments.

A novel electrospinning setup for the fabrication of thickness-controllable 3D scaffolds with an ordered nanofibrous structure

Electrospinning is a popular nanotechnology used to produce fibrous scaffolds from a wide range of materials. For tissue regeneration and bioengineering applications, there is a growing interest in fabricating tailored 3D scaffolds with a complex tissue-like structure, i.e., nanometer diameter, aligned fibers and controllable thickness that may be suitable for specific organs and tissues. However, conventional electrospinning techniques can only produce either 2D aligned nanofibrous structures with limited thickness or 3D fibrous scaffolds with disordered fibrous structures. In this study, a novel electrospinning setup using a parallel double thin plate collector device and a separate fiber removal device was developed to generate 3D electrospun scaffolds with aligned nanofibers and controllable thickness. As a demonstration, the formation mechanism of the ordered fibrous structure was analyzed, and polyvinyl alcohol (PVA) was processed into fibrous scaffolds. The nanofibrous membranes possessed a high alignment degree with approximately 76% of the fibers within ±5° and tailored thicknesses from 69.6 to 1144.9μm.

Activation of Transcription Factor GAX and Concomitant Downregulation of IL-1β and ERK1/2 Modulate Vascular Smooth Muscle Cell Phenotype in 3D Fibrous Scaffolds.

Since vascular smooth muscle cells (VSMCs) display phenotypic plasticity in response to changing environmental cues, understanding the molecular mechanisms underlying the phenotypic modulation mediated by a three-dimensional (3D) scaffold is important to engineer functional vasculature. Following cell seeding into 3D scaffolds, the synthetic phenotype is desired to enable cells to expand rapidly and produce and assemble extracellular matrix components, but must revert to a quiescent contractile phenotype after tissue fabrication to impart the contractile properties found in native blood vessels. This study shows that 3D electrospun fibrous scaffolds regulate human coronary artery smooth muscle cells (HCASMCs) toward a more synthetic phenotype characterized by reduced contractile markers, such as smooth muscle alpha-actin and calponin. The reduction in contractile markers expression was mediated by endogenously expressed proinflammatory cytokine interleukin-1β (IL-1β). 3D topography transiently induces concomitant upregulation of IL-1β and MAPK ERK1/2 through nuclear factor-κB-dependent signaling pathway. An early burst of expression of IL-1β is essential for suppression of the homeobox transcription factor Gax and related cyclin-dependent kinase inhibitor p21(Cip1), which are key regulators for cells exiting from cell cycle. Our findings provide new insights for understanding signaling mechanisms of HCASMCs in electrospun 3D fibrous scaffolds, which have considerable value for application in vascular tissue engineering.

Effect of fiber diameter on the assembly of functional 3D cardiac patches

The cardiac ECM has a unique 3D structure responsible for tissue morphogenesis and strong contractions. It is divided into three fiber groups with specific roles and distinct dimensions; nanoscale endomysial fibers, perimysial fibers with a diameter of 1 μm, and epimysial fibers, which have a diameter of several micrometers. We report here on our work, where distinct 3D fibrous scaffolds, each of them recapitulating the dimension scales of a single fiber population in the heart matrix, were fabricated. We have assessed the mechanical properties of these scaffolds and the contribution of each fiber population to cardiomyocyte morphogenesis, tissue assembly and function. Our results show that the nanoscale fiber scaffolds were more elastic than the microscale scaffolds, however, cardiomyocytes cultured on microscale fiber scaffolds exhibited enhanced spreading and elongation, both on the single cell and on the engineered tissue levels. In addition, lower fibroblast proliferation rates were observed on these microscale topographies. Based on the collected data we have fabricated composite scaffolds containing micro and nanoscale fibers, promoting superior tissue morphogenesis without compromising tissue contraction. Cardiac tissues, engineered within these composite scaffolds exhibited superior function, including lower excitation threshold and stronger contraction forces than tissue engineered within the single-population fiber scaffolds.

Reinforcement of Mono- and Bi-layer Poly(Ethylene Glycol) Hydrogels with a Fibrous Collagen Scaffold.

Biomaterial-based tissue engineering strategies hold great promise for osteochondral tissue repair. Yet significant challenges remain in joining highly dissimilar materials to achieve a biomimetic, mechanically robust design for repairing interfaces between soft tissue and bone. This study sought to improve interfacial properties and function in a bi-layer hydrogel interpenetrated with a fibrous collagen scaffold. 'Soft' 10% (w/w) and 'stiff' 30% (w/w) PEGDM was formed into mono- or bi-layer hydrogels possessing a sharp diffusional interface. Hydrogels were evaluated as single-(hydrogel only) or multi-phase (hydrogel + fibrous scaffold penetrating throughout the stiff layer and extending >500 μm into the soft layer). Including a fibrous scaffold into both soft and stiff mono-layer hydrogels significantly increased tangent modulus and toughness and decreased lateral expansion under compressive loading. Finite element simulations predicted substantially reduced stress and strain gradients across the soft-stiff hydrogel interface in multi-phase, bilayer hydrogels. When combining two low moduli constituent materials, composites theory poorly predicts the observed, large modulus increases. These results suggest material structure associated with the fibrous scaffold penetrating within the PEG hydrogel as the major contributor to improved properties and function-the hydrogel bore compressive loads and the 3D fibrous scaffold was loaded in tension thus resisting lateral expansion.

Strategies for regeneration of components of nervous system: scaffolds, cells and biomolecules.

Nerve diseases including acute injury such as peripheral nerve injury (PNI), spinal cord injury (SCI) and traumatic brain injury (TBI), and chronic disease like neurodegeneration disease can cause various function disorders of nervous system, such as those relating to memory and voluntary movement. These nerve diseases produce great burden for individual families and the society, for which a lot of efforts have been made. Axonal pathways represent a unidirectional and aligned architecture allowing systematic axonal development within the tissue. Following a traumatic injury, the intricate architecture suffers disruption leading to inhibition of growth and loss of guidance. Due to limited capacity of the body to regenerate axonal pathways, it is desirable to have biomimetic approach that has the capacity to graft a bridge across the lesion while providing optimal mechanical and biochemical cues for tissue regeneration. And for central nervous system injury, one more extra precondition is compulsory: creating a less inhibitory surrounding for axonal growth. Electrospinning is a cost-effective and straightforward technique to fabricate extracellular matrix (ECM)-like nanofibrous structures, with various fibrous forms such as random fibers, aligned fibers, 3D fibrous scaffold and core-shell fibers from a variety of polymers. The diversity and versatility of electrospinning technique, together with functionalizing cues such as neurotrophins, ECM-based proteins and conductive polymers, have gained considerable success for the nerve tissue applications. We are convinced that in the future the stem cell therapy with the support of functionalized electrospun nerve scaffolds could be a promising therapy to cure nerve diseases.

Physical and biological activities of newly designed, macro-pore-structure-controlled 3D fibrous poly(ε-caprolactone)/hydroxyapatite composite scaffolds

A 3D fibrous scaffold using an electrohydrodynamic jet process supplemented with in vitro mineralization to obtain a hydroxyapatite layer in simulated body fluid was fabricated.

Water-stable three-dimensional ultrafine fibrous scaffolds from keratin for cartilage tissue engineering.

Intrinsically water-stable scaffolds composed of ultrafine keratin fibers oriented randomly and evenly in three dimensions were electrospun for cartilage tissue engineering. Keratin has been recognized as a biomaterial that could substantially support the growth and development of multiple cell lines. Besides, three-dimensional (3D) ultrafine fibrous structures were preferred in tissue engineering due to their structural similarity to native extracellular matrices in soft tissues. Recently, we have developed a nontraditional approach to developing 3D fibrous scaffolds from alcohol-soluble corn protein, zein, and verified their structural advantages in tissue engineering. However, keratin with highly cross-linked molecular structures could not be readily dissolved in common solvents for fiber spinning, which required the remarkable drawability of solution. So far, 3D fibrous scaffolds from pure keratin for biomedical applications have not been reported. In this research, the highly cross-linked keratin from chicken feathers was de-cross-linked and disentangled into linear and aligned molecules with preserved molecular weights, forming highly stretchable spinning dope. The solution was readily electrospun into scaffolds with ultrafine keratin fibers oriented randomly in three dimensions. Due to the highly cross-linked molecular structures, keratin scaffolds showed intrinsic water stability. Adipose-derived mesenchymal stem cells could penetrate much deeper, proliferate, and chondrogenically differentiate remarkably better on the 3D keratin scaffolds than on 2D PLA fibrous scaffolds, 3D soy protein fibrous scaffolds, or 3D commercial nonfibrous scaffolds. In summary, the electrospun 3D ultrafine fibrous scaffolds from keratin could be promising candidates for cartilage tissue engineering.