Fabrication of highly aligned fibrous scaffolds for tissue regeneration by centrifugal spinning technology

Biomimetic fiber/hydrogel composite scaffolds based on chitosan hydrogel and surface modified PCL chopped-microfibers

Hydrogel/fiber composites have received wide attention as tissue engineering scaffolds due to the outstanding properties of fibers and hydrogels. In the current research, a hydrogel/fiber composite scaffold was made based on chitosan-modified polycaprolactone (PCL) microfibers and chitosan hydrogel as a binder. The presence of chitosan as a modifier on the surface of fibers and as a binder between fibers can create scaffolds with excellent structural and mechanical properties. To this end, the three-dimensional microfibers were first functionalized with amine groups. Then, the chitosan chains were attached to the fibers by an aldehyde coupling agent and Schiff base reaction. FTIR and Raman spectroscopies corroborated that chitosan was successfully immobilized on PCL fibers. Chitosan-modified fibers were molded with chitosan solutions of various concentrations and the prepared composite scaffolds were stabilized using ionic crosslinking. The obtained composites represented a porous 3D structure with highly interconnected pores. The compressive modulus increased by 19 and 2.7 folds and the tensile modulus was augmented by 28 and 4 folds, in respective dry and swollen states with increasing hydrogel concentration from 0.1 to 1 %. Hydrogel/fiber composites were able to preserve cell viability, and increasing the hydrogel proportion increased adhesion, proliferation and penetration of cells into the scaffold.

Metal Cross-Linked Supramolecular Gel Noodles: Structural Insights and Antibacterial Assessment

Achieving precise control over gelator alignment and morphology is crucial for crafting tailored materials and supramolecular structures with distinct properties. We successfully aligned the self-assembled micelles formed by a functionalized dipeptide 2NapFF into long 1-D "gel noodles" by cross-linking with divalent metal chlorides. We identify the most effective cross-linker for alignment, enhancing mechanical stability, and imparting functional properties. Our study shows that Group 2 metal ions are particularly suited for creating mechanically robust yet flexible gel noodles because of their ionic and nondirectional bonding with carboxylate groups. In contrast, the covalent nature and high directional bonds of d-block metal ions with carboxylates tend to disrupt the self-assembly of 2NapFF. Furthermore, the 2NapFF-Cu noodles demonstrated selective antibacterial activity, indicating that the potent antibacterial property of the copper(II) ion is preserved within the cross-linked system. By merging insights into molecular alignment, gel extrusion processing, and integrating specific functionalities, we illustrate how the versatility of dipeptide-based gels can be utilized in creating next-generation soft materials.

Porous biomaterial scaffolds for skeletal muscle tissue engineering

Volumetric muscle loss is a traumatic injury which overwhelms the innate repair mechanisms of skeletal muscle and results in significant loss of muscle functionality. Tissue engineering seeks to regenerate these injuries through implantation of biomaterial scaffolds to encourage endogenous tissue formation and to restore mechanical function. Many types of scaffolds are currently being researched for this purpose. Scaffolds are typically made from either natural, synthetic, or conductive polymers, or any combination therein. A major criterion for the use of scaffolds for skeletal muscle is their porosity, which is essential for myoblast infiltration and myofiber ingrowth. In this review, we summarize the various methods of fabricating porous biomaterial scaffolds for skeletal muscle regeneration, as well as the various types of materials used to make these scaffolds. We provide guidelines for the fabrication of scaffolds based on functional requirements of skeletal muscle tissue, and discuss the general state of the field for skeletal muscle tissue engineering.

Nanofibers in Ocular Drug Targeting and Tissue Engineering: Their Importance, Advantages, Advances, and Future Perspectives

Nanofibers are frequently encountered in daily life as a modern material with a wide range of applications. The important advantages of production techniques, such as being easy, cost effective, and industrially applicable are important factors in the preference for nanofibers. Nanofibers, which have a broad scope of use in the field of health, are preferred both in drug delivery systems and tissue engineering. Due to the biocompatible materials used in their construction, they are also frequently preferred in ocular applications. The fact that they have a long drug release time as a drug delivery system and have been used in corneal tissue studies, which have been successfully developed in tissue engineering, stand out as important advantages of nanofibers. This review examines nanofibers, their production techniques and general information, nanofiber-based ocular drug delivery systems, and tissue engineering concepts in detail.

Recent Advances in Centrifugal Spinning and Their Applications in Tissue Engineering

Over the last decade, researchers have investigated the potential of nano and microfiber scaffolds to promote wound healing, tissue regeneration, and skin protection. The centrifugal spinning technique is favored over others due to its relatively straightforward mechanism for producing large quantities of fiber. Many polymeric materials have yet to be investigated in search of those with multifunctional properties that would make them attractive in tissue applications. This literature presents the fundamental process of fiber generation, and the effects of fabrication parameters (machine, solution) on the morphologies such as fiber diameter, distribution, alignment, porous features, and mechanical properties. Additionally, a brief discussion is presented on the underlying physics of beaded morphology and continuous fiber formation. Consequently, the study provides an overview of the current advancements in centrifugally spun polymeric fiber-based materials and their morphological features, performance, and characteristics for tissue engineering applications.

Polymeric Gel Scaffolds and Biomimetic Environments for Wound Healing

Infected wounds that do not heal are a worldwide problem that is worsening, with more people dying and more money being spent on care. For any disease to be managed effectively, its root cause must be addressed. Effective wound care becomes a bigger problem when various traditional wound healing methods and products may not only fail to promote good healing. Still, it may also hinder the healing process, causing wounds to stay open longer. Progress in tissue regeneration has led to developing three-dimensional scaffolds (3D) or constructs that can be leveraged to facilitate cell growth and regeneration while preventing infection and accelerating wound healing. Tissue regeneration uses natural and fabricated biomaterials that encourage the growth of tissues or organs. Even though the clinical need is urgent, the demand for polymer-based therapeutic techniques for skin tissue abnormalities has grown quickly. Hydrogel scaffolds have become one of the most imperative 3D cross-linked scaffolds for tissue regeneration because they can hold water perfectly and are porous, biocompatible, biodegradable, and biomimetic. For damaged organs or tissues to heal well, the porosity topography of the natural extracellular matrix (ECM) should be imitated. This review details the scaffolds that heal wounds and helps skin tissue to develop. After a brief overview of the bioactive and drug-loaded polymeric hydrogels, the discussion moves on to how the scaffolds are made and what they are made of. It highlights the present uses of in vitro and in-vivo employed biomimetic scaffolds. The prospects of how well bioactiveloaded hydrogels heal wounds and how nanotechnology assists in healing and regeneration have been discussed.

Rotary Jet Spinning (RJS): A Key Process to Produce Biopolymeric Wound Dressings

Wounds result from different causes (e.g., trauma, surgeries, and diabetic ulcers), requiring even extended periods of intensive care for healing, according to the patient's organism and treatment. Currently, wound dressings generated by polymeric fibers at micro and nanometric scales are promising for healing the injured area. They offer great surface area and porosity, mimicking the fibrous extracellular matrix structure, facilitating cell adhesion, migration, and proliferation, and accelerating the wound healing process. Such properties resulted in countless applications of these materials in biomedical and tissue engineering, also as drug delivery systems for bioactive molecules to help tissue regeneration. The techniques used to engineer these fibers include spinning methods (electro-, rotary jet-), airbrushing, and 3D printing. These techniques have important advantages, such as easy-handle procedure and process parameters variability (type of polymer), but encounter some scalability problems. RJS is described as a simple and low-cost technique resulting in high efficiency and yield for fiber production, also capable of bioactive agents' incorporation to improve the healing potential of RJS wound dressings. This review addresses the use of RJS to produce polymeric fibers, describing the concept, type of configuration, comparison to other spinning techniques, most commonly used polymers, and the relevant parameters that influence the manufacture of the fibers, for the ultimate use in the development of wound dressings.

An Overview of Recent Progress in Nanofiber Membranes for Oily Wastewater Treatment

Oil separation from water becomes a challenging issue in industries, especially when large volumes of stable oil/water emulsion are discharged. The present short review offers an overview of the recent developments in the nanofiber membranes used in oily wastewater treatment. This review notes that nanofiber membranes can efficiently separate the free-floating oil, dispersed oil and emulsified oil droplets. The highly interconnected pore structure nanofiber membrane and its modified wettability can enhance the permeation flux and reduce the fouling. The nanofiber membrane is an efficient separator for liquid-liquid with different densities, which can act as a rejector of either oil or water and a coalescer of oil droplets. The present paper focuses on nanofiber membranes' production techniques, nanofiber membranes' modification for flux and separation efficiency improvement, and the future direction of research, especially for practical developments.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Large-Scale Centrifugal Multispinning Production of Polymer Micro- and Nanofibers for Mask Filter Application with a Potential of Cospinning Mixed Multicomponent Fibers

Recently, the polymer nanofiber web is in high demand as a strong barrier against harmful particles due to its high capture efficiency and strong droplet-blocking ability. As an advanced spinning technique, the centrifugal multispinning system was designed by sectioning a rotating disk into triple subdisks, showing mass producibility of polymer nanofibers with cospinning ability. Using the system, gram-scale production of polystyrene (PS), poly(methyl methacrylate), and polyvinylpyrrolidone (PVP) was demonstrated, showing a possibility for versatile use of the system. Moreover, a high production rate of ∼25 g/h for PS nanofibers was achieved, which is ∼300× higher than that of the usual electrospinning process. Utilizing the cospinning ability, we controlled the contact angle and electrostatic charge of the multicomponent nanofiber web by adjusting the relative amounts of PS and PVP fibers, showing a potential for functional textile application. With the fabricated PS nanofiber-based filters, we achieved high capture efficiency up to ∼97% with outstanding droplet-blocking ability.

A dual-phase scaffold produced by rotary jet spinning and electrospinning for tendon tissue engineering

Tendon is a highly hierarchical and oriented tissue that provides high mechanical strength. Tendon injuries lead to loss of function, disability, and a decrease in quality of life. The limited healing capacity of tendon tissue leads to scar tissue formation, which can affect mechanical strength and cause a re-tear. Tissue engineering can be the solution to achieving complete and proper healing of tendon. The developed constructs should be mechanically strong while maintaining a suitable environment for cell proliferation. In this study, a dual-phase fibrous scaffold was produced by combining fibrous mats produced by rotary jet spinning (RJS) and wet electrospinning (WES), with the intent of improving the healing capacity of the construct. Dual-phase scaffolds were formed from aligned poly(ϵ-caprolactone) (PCL) fibers (Shell) produced by RJS and randomly oriented PCL or PCL/gelatin fibers (Core) produced by WES systems. The scaffolds mimicked i) the repair phase of tendon healing, in which randomly-oriented collagen type III is deposited by randomly-oriented WES fibers and ii) the remodeling stage, in which aligned collagen type I fibers are deposited by aligned RJS fibers. In vitro studies showed that the presence of randomly-oriented core fibers inside the aligned PCL fiber shell of the dual-phase scaffold increased the initial attachment and viability of cells. Scanning electron microscopy and confocal microscopy analysis showed that the presence of aligned RJS fibers supported the elongation of cells through aligned fibers which improves tendon tissue healing by guiding oriented cell proliferation and extracellular matrix deposition. Tenogenic differentiation of human adipose-derived mesenchymal stem cells on scaffolds was studied when supplemented with growth differentiation factor 5 (GDF-5). GDF-5 treatment improved the viability, collagen type III deposition and scaffold penetration of human adipose derived stem cells. The developed FSPCL/ESPCL-Gel 3:1 scaffold (FS = centrifugal force spinning/RJS, ES = wet electrospinning, Gel = gelatin) sustained high mechanical strength, and improved cell viability and orientation while supporting tenogenic differentiation.

A Critical Review on the Production of Electrospun Nanofibres for Guided Bone Regeneration in Oral Surgery

Nanofibre-based membranes or scaffolds exhibit high surface-to-volume ratio, which allows an improved cell adhesion, representing an attractive subgroup of biomaterials due to their unique properties. Among several techniques of nanofiber production, electrospinning is a cost-effective technique that has been, to date, attractive for several medical applications. Among these, guided bone regeneration is a surgical procedure in which bone regeneration, due to bone atrophy following tooth loss, is "guided" by an occlusive barrier. The membrane should protect the initial blood clot from any compression, shielding the bone matrix during maturation from infiltration of soft tissues cells. This review will focus its attention on the application of electrospinning (ELS) in oral surgery bone regeneration. Despite the abundance of published papers related to the electrospinning technique applied in the field of bone regeneration of the jaws, to the authors' knowledge, no articles report clinical application of these structures. Moreover, only a few records can be found with in vivo application. Therefore, no human studies have to date been detectable. New approaches such as multifunctional multilayering and coupling with bone promoting factors or antimicrobial agents, makes this technology very attractive. However, greater efforts should be made by researchers and companies to turn these results into clinical practice.

Recent advances in biomaterials for 3D scaffolds: A review

Considering the advantages and disadvantages of biomaterials used for the production of 3D scaffolds for tissue engineering, new strategies for designing advanced functional biomimetic structures have been reviewed. We offer a comprehensive summary of recent trends in development of single- (metal, ceramics and polymers), composite-type and cell-laden scaffolds that in addition to mechanical support, promote simultaneous tissue growth, and deliver different molecules (growth factors, cytokines, bioactive ions, genes, drugs, antibiotics, etc.) or cells with therapeutic or facilitating regeneration effect. The paper briefly focuses on divers 3D bioprinting constructs and the challenges they face. Based on their application in hard and soft tissue engineering, in vitro and in vivo effects triggered by the structural and biological functionalized biomaterials are underlined. The authors discuss the future outlook for the development of bioactive scaffolds that could pave the way for their successful imposing in clinical therapy.

Needleless electrospun and centrifugal spun poly-ε-caprolactone scaffolds as a carrier for platelets in tissue engineering applications: A comparative study with hMSCs

The biofunctionalization of scaffolds for tissue engineering is crucial to improve the results of regenerative therapies. This study compared the effect of platelet-functionalization of 2D electrospun and 3D centrifugal spun scaffolds on the osteogenic potential of hMSCs. Scaffolds prepared from poly-ε-caprolactone, using electrospinning and centrifugal spinning technology, were functionalized using five different concentrations of platelets. Cell proliferation, metabolic activity and osteogenic differentiation were tested using hMSCs cultured in differential and non-differential medium. The porous 3D structure of the centrifugal spun fibers resulted in higher cell proliferation. Furthermore, the functionalization of the scaffolds with platelets resulted in a dose-dependent increase in cell metabolic activity, proliferation and production of an osteogenic marker - alkaline phosphatase. The effect was further promoted by culture in an osteogenic differential medium. The increase in combination of both platelets and osteogenic media shows an improved osteoinduction by platelets in environments rich in inorganic phosphate and ascorbate. Nevertheless, the results of the study showed that the optimal concentration of platelets for induction of hMSC osteogenesis is in the range of 900-3000 × 10⁹ platelets/L. The study determines the potential of electrospun and centrifugal spun fibers with adhered platelets, for use in bone tissue engineering.

The fabrication of biomineralized fiber-aligned PLGA scaffolds and their effect on enhancing osteogenic differentiation of UCMSC cells

The key factor of scaffold design for bone tissue engineering is to mimic the microenvironment of natural bone extracellular matrix (ECM) and guide cell osteogenic differentiation. The biomineralized fiber-aligned PLGA scaffolds (a-PLGA/CaPs) was developed in this study by mimicking the structure and composition of native bone ECM. The aligned PLGA fibers was prepared by wet spinning and then biomineralized via an alternate immersion method. Introduction of a bioceramic component CaP onto the PLGA fibers led to changes in surface roughness and hydrophilicity, which showed to modulate cell adhesion and cell morphology of umbilical cord mesenchymal stem cells (UCMSCs). It was found that organized actin filaments of UCMSCs cultured on both a-PLGA and a-PLGA/CaP scaffolds appeared to follow contact guidance along the aligned fibers, and those cells grown on a-PLGA/CaP scaffolds exhibited a more polarized cellular morphology. The a-PLGA/CaP scaffold with multicycles of mineralization facilitated the cell attachment on the fiber surfaces and then supported better cell adhesion and contact guidance, leading to enhancement in following proliferation and osteogenic differentiation of UCMSCs. Our results give some insights into the regulation of cell behaviors through design of ECM-mimicking structure and composition and provide an alternative wet-spun fiber-aligned scaffold with HA-mineralized layer for bone tissue engineering application.

Protein-Based Fiber Materials in Medicine: A Review

Fibrous materials have garnered much interest in the field of biomedical engineering due to their high surface-area-to-volume ratio, porosity, and tunability. Specifically, in the field of tissue engineering, fiber meshes have been used to create biomimetic nanostructures that allow for cell attachment, migration, and proliferation, to promote tissue regeneration and wound healing, as well as controllable drug delivery. In addition to the properties of conventional, synthetic polymer fibers, fibers made from natural polymers, such as proteins, can exhibit enhanced biocompatibility, bioactivity, and biodegradability. Of these proteins, keratin, collagen, silk, elastin, zein, and soy are some the most common used in fiber fabrication. The specific capabilities of these materials have been shown to vary based on their physical properties, as well as their fabrication method. To date, such fabrication methods include electrospinning, wet/dry jet spinning, dry spinning, centrifugal spinning, solution blowing, self-assembly, phase separation, and drawing. This review serves to provide a basic knowledge of these commonly utilized proteins and methods, as well as the fabricated fibers’ applications in biomedical research.

Centrifugally Spun Recycled PET: Processing and Characterization

Centrifugal spinning, which is a high-productivity fiber fabrication technique, was used to produce a value-added product from recycled poly(ethylene terephthalate) (rPET). In the present study, rPET fibers, with fiber diameters ranging from submicron to micrometer in scale, were fabricated by spinning a solution of rPET in a mixture of dichloromethane and trifluoroacetic acid. The influence of the polymer solution concentration (the viscosity), the rotational speed of the spinneret, and the inner diameter of the needles on the formation and morphology and mechanical properties of the fibers were examined through scanning electron microscopy and using a tensile testing machine. The thermal behaviors of fibrous mats with various average diameters were also investigated through differential scanning calorimetry. The smoothest and smallest fibers, with an average diameter of 619 nm, were generated using an rPET solution of 10 wt % under a rotation speed of 15,000 rpm using needles having an inner diameter of 160 μm. The fibrous mats have an average tensile strength and modulus of 4.3 MPa and 34.4 MPa, respectively. The productivity and the mechanical properties indicate that centrifugal spinning is an effective technique to fabricate high-value product from rPET.

Electrospun protein nanofibers in healthcare: A review

Electrospun nanofibers are being utilized for a wide range of healthcare applications. A plethora of natural and synthetic polymers are exploited for their ability to be electrospun and replace the complex habitat provided by the extracellular matrix for the cells. The fabrication of nanofibers can be tuned to act as a multicarrier system to deliver drugs, growth factors and health supplements etc. in a sustained manner. Owing to its pliability, nanofibers reached its heights in tissue engineering and drug delivery applications. This review mainly focuses on various standardized parameters and optimized blending ratios for animal and plant proteins to yield fine, continuous nanofibers for effective utilization in various healthcare applications.

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.

A comparison of high throughput core–shell 2D electrospinning and 3D centrifugal spinning techniques to produce platelet lyophilisate-loaded fibrous scaffolds and their effects on skin cells

Nanofibres enriched with bioactive molecules, as actively acting scaffolds, play an important role in tissue engineering.

Emulsion centrifugal spinning for production of 3D drug releasing nanofibres with core/shell structure

Herein we describe the core/shell centrifugal spinning process to deliver susceptible bioactive molecules.

A Controlled Design of Aligned and Random Nanofibers for 3D Bi-functionalized Nerve Conduits Fabricated via a Novel Electrospinning Set-up

Scaffolds made of aligned nanofibers are favorable for nerve regeneration due to their superior nerve cell attachment and proliferation. However, it is challenging not only to produce a neat mat or a conduit form with aligned nanofibers but also to use these for surgical applications as a nerve guide conduit due to their insufficient mechanical strength. Furthermore, no studies have been reported on the fabrication of aligned nanofibers and randomly-oriented nanofibers on the same mat. In this study, we have successfully produced a mat with both aligned and randomly-oriented nanofibers by using a novel electrospinning set up. A new conduit with a highly-aligned electrospun mat is produced with this modified electrospinning method, and this proposed conduit with favorable features, such as selective permeability, hydrophilicity and nerve growth directional steering, were fabricated as nerve guide conduits (NGCs). The inner surface of the nerve conduit is covered with highly aligned electrospun nanofibers and is able to enhance the proliferation of neural cells. The central part of the tube is double-coated with randomly-oriented nanofibers over the aligned nanofibers, strengthening the weak mechanical strength of the aligned nanofibers.

A review on non-electro nanofibre spinning techniques

A large surface area, scalable porosity, and versatility have made nanofibres one of the most widely investigated morphologies among the nanomaterials.